Method for transmitting and receiving synchronization signal block in unlicensed band, and device therefor

ABSTRACT

Disclosed is a method by which a terminal receives a synchronization signal/physical broadcast channel (SS/PBCH) block in an unlicensed band. Particularly, the method comprises: receiving information related to an actual transmitted SS/PBCH block (ATSS) transmitted by a base station; and receiving the SS/PBCH block on the basis of valid bits from among a plurality of bits included in the information related to the ATSS, wherein the number of valid bits can be based on an interval value between SS/PBCH blocks capable of assuming a quasi co-location (QCL).

TECHNICAL FIELD

The present disclosure relates to a method of transmitting and receiving a synchronization signal block in an unlicensed band and device therefor, and more particularly, to a method of indicating the index of a synchronization signal block actually transmitted in an unlicensed band and device therefor.

BACKGROUND

5G is a technique for providing a stream rated at hundreds of megabits per second to gigabytes per second and may complement fiber-to-the-home (FTTH) and cable-based broadband (or DOCSIS). Such a high speed may be required to provide not only virtual reality (VR) and augmented reality (AR) but also television (TV) services with a resolution of 4K or higher (6K, 8K, or higher). VR and AR applications mostly include immersive sporting events. A specific application may require a special network configuration. For example, for a VR game, a game company may need to integrate a core server with an edge network server of a network operator in order to minimize latency.

The automotive sector is expected to be an important new driver for 5G with many use cases for vehicle mobile communication. For example, entertainment for passengers requires high-capacity and high-mobility broadband at the same time because future users expect to continue high quality of connections independently of their locations and speeds. Another use case in the automotive field is an AR dashboard. The AR dashboard identifies an object in the dark and tells a driver about the distance and movement of the object, that is, displays overlay information on top of what the driver is seeing through the front window. In the future, wireless modules enable communication between vehicles, information exchange between vehicles and supporting infrastructures, and information exchange between vehicles and other connected devices (e.g., device accompanied by pedestrians). A safety system guides alternative driving courses so that drivers may drive safely to reduce the risk of accidents. The next step would be a remote control vehicle or a self-driving vehicle, which requires exceptionally reliable and extremely fast communication between different self-driving vehicles and between vehicles and infrastructures. In the future, the self-driving vehicle will perform all driving activities, and the driver will focus only on traffic problems that the vehicle cannot autonomously identify. Technical requirements of the self-driving vehicle are ultra-low latency, ultra-high speed, and high reliability to increase traffic safety to levels that humans cannot achieve.

In a smart city and a smart home, which is called a smart society, a high-density wireless sensor network will be embedded. A distributed network of intelligent sensors will identify conditions for cost and energy-efficient maintenance of a city or house. Similar settings may be established for each home. Temperature sensors, window and heating controllers, security systems, and home appliances are all wirelessly connected. Although many of these sensors have typically low data rates, low power, and low cost, real-time high-definition video may be required in a particular type of device for monitoring.

Since consumption and distribution of energy including heat or gas is highly decentralized, automatic control of a distributed sensor network is required. A smart grid collects information and interconnects sensors using digital information and communication technology to operate the sensors based on the collected information. Such information may include the behavior of suppliers and consumers, thus enabling the smart grid to improve the distribution of fuel such as electricity, in efficient, reliable, economical, production-sustainable, and automatic manners. The smart grid may be considered as a sensor network with low latency.

The health sector has a large number of applications that may benefit from mobile communication. Communication systems may support telemedicine, that is, provide medical care in remote areas. Telemedicine may help to reduce a distance barrier and improve access to medical services that are not continuously available in distant rural areas. Telemedicine is also used to save lives in critical treatment and emergency situations. A wireless sensor network based on mobile communication may provide remote monitoring and sensors for parameters, such as heart rate and blood pressure.

Wireless and mobile communication gradually becomes important in industrial applications. Wiring involves high costs for installation and maintenance. Thus, the possibility of replacing a cable by a reconfigurable wireless link is attractive for many industrial fields. However, to this end, a wireless connection needs to operate with similar latency, reliability, and capacity to those of a cable. In addition, the maintenance thereof also needs to be simplified. Low latency and low error probabilities are new requirements for 5G connections.

Logistics and freight tracking are important use cases for mobile communication that enables the tracking of inventory and packages wherever they are through location-based information systems. The logistics and freight use cases typically require lower data rates but need wide coverage and reliable location information.

SUMMARY

The object the present disclosure is to provide a method of transmitting and receiving a synchronization signal block in an unlicensed band and device therefor.

It will be appreciated by persons skilled in the art that the objects that could be achieved with the present disclosure are not limited to what has been particularly described hereinabove and the above and other objects that the present disclosure could achieve will be more clearly understood from the following detailed description.

In an aspect of the present disclosure, a method of receiving, by a user equipment (UE), a synchronization signal/physical broadcast channel (SS/PBCH) block in an unlicensed band is provided. The method may include: receiving information on an actual transmitted SS/PBCH block (ATSS) transmitted from a base station; and receiving the SS/PBCH block based on valid bits among a plurality of bits included in the information on the ATSS. The number of valid bits may be based on an interval between SS/PBCH blocks in which a quasi co-location (QCL) assumption is allowed.

Among the plurality of bits, bits except the valid bits may not be interpreted.

Among the plurality of bits, bits except the valid bits may have a value of ‘0’.

The number of valid bits may be equal to the interval between the SS/PBCH blocks in which the QCL assumption is allowed.

The method may further include performing rate matching for a physical downlink shared channel (PDSCH) or mapping between the SS/PBCH block and a random access channel (RACH) occasion based on the valid bits.

The number of valid bits may be equivalent to the number of SS/PBCH indices for the unlicensed band, and the valid bits may include as many bits as the number of the SS/PBCH block indices from a first bit among the plurality of bits.

The UE may be configured to communicate with at least one of the base station, a UE other than the UE, a network, or an autonomous driving vehicle.

In another aspect of the present disclosure, a device configured to receive an SS/PBCH block in an unlicensed band is provided. The device may include: at least one processor; and at least one memory operably connected to the at least one processor and configured to store instructions that, when executed, cause the at least one processor to perform operations including: receiving information on an ATSS transmitted from a base station; and receiving the SS/PBCH block based on valid bits among a plurality of bits included in the information on the ATSS. The number of valid bits may be based on an interval between SS/PBCH blocks in which a QCL assumption is allowed.

Among the plurality of bits, bits except the valid bits may not be interpreted.

Among the plurality of bits, bits except the valid bits may have a value of ‘0’.

The number of valid bits may be equal to the interval between the SS/PBCH blocks in which the QCL assumption is allowed.

The operations may further include performing rate matching for a PDSCH or mapping between the SS/PBCH block and a RACH occasion based on the valid bits.

The number of valid bits may be equivalent to the number of SS/PBCH indices for the unlicensed band, and the valid bits may include as many bits as the number of the SS/PBCH block indices from a first bit among the plurality of bits.

The device may be configured to communicate with at least one of the base station, a UE, a network, or an autonomous driving vehicle.

In a further aspect of the present disclosure, a UE configured to receive an SS/PBCH block in an unlicensed band is provided. The UE may include: at least one transceiver; at least one processor; and at least one memory operably connected to the at least one processor and configured to store instructions that, when executed, cause the at least one processor to perform operations including: receiving information on an ATSS transmitted from a base station through the at least one transceiver; and receiving the SS/PBCH block through the at least one transceiver based on valid bits among a plurality of bits included in the information on the ATSS. The number of valid bits may be based on an interval between SS/PBCH blocks in which a QCL assumption is allowed.

According to the present disclosure, a synchronization signal block actually transmitted in an unlicensed band may be efficiently indicated.

It will be appreciated by persons skilled in the art that the effects that can be achieved with the present disclosure are not limited to what has been particularly described hereinabove and other advantages of the present disclosure will be more clearly understood from the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 to 4 illustrate examples of various wireless devices to which embodiments of the present disclosure are applied.

FIG. 5 illustrates an exemplary signal processing circuit to which embodiments of the present disclosure are applied.

FIG. 6 is a diagram illustrating the control-plane and user-plane architecture of radio interface protocols between a user equipment (UE) and an evolved UMTS terrestrial radio access network (E-UTRAN) in conformance to a 3rd generation partnership project (3GPP) radio access network standard.

FIG. 7 is a diagram illustrating analog beamforming in a new radio access technology (new RAT or NR) system.

FIGS. 8 to 12 are diagrams for explaining beam management in the NR system.

FIGS. 13 and 14 are diagrams for explaining downlink channel transmission in an unlicensed band.

FIGS. 15, 16, 17, 18, 19 and 20 are diagrams illustrating the composition of a synchronization signal/physical broadcast channel (SS/PBCH) block and a method of transmitting an SS/PBCH block.

FIG. 21 is a diagram illustrating an exemplary random access procedure.

FIGS. 22, 23 and 24 are diagrams illustrating structures of a radio frame and slots used in the NR system.

FIGS. 25, 26 and 27 are diagrams illustrating operations of a UE, a base station, and a network according to the present disclosure.

FIGS. 28 to 33 are diagrams illustrating particular embodiments of mapping the index of an SS/PBCH block in an unlicensed band according to the present disclosure.

FIG. 34 illustrates an example of a communication system to which embodiments of the present disclosure are applied.

DETAILED DESCRIPTION

The configuration, operation, and other features of the present disclosure will readily be understood with embodiments of the present disclosure described with reference to the attached drawings. Embodiments of the present disclosure as set forth herein are examples in which the technical features of the present disclosure are applied to a 3rd generation partnership project (3GPP) system.

While embodiments of the present disclosure are described in the context of long term evolution (LTE) and LTE-advanced (LTE-A) systems, they are purely exemplary. Therefore, the embodiments of the present disclosure are applicable to any other communication system as long as the above definitions are valid for the communication system.

The term, base station (BS) may be used to cover the meanings of terms including remote radio head (RRH), evolved Node B (eNB or eNode B), transmission point (TP), reception point (RP), relay, and so on.

The 3GPP communication standards define downlink (DL) physical channels corresponding to resource elements (REs) carrying information originated from a higher layer, and DL physical signals which are used in the physical layer and correspond to REs which do not carry information originated from a higher layer. For example, physical downlink shared channel (PDSCH), physical broadcast channel (PBCH), physical multicast channel (PMCH), physical control format indicator channel (PCFICH), physical downlink control channel (PDCCH), and physical hybrid ARQ indicator channel (PHICH) are defined as DL physical channels, and reference signals (RSs) and synchronization signals (SSs) are defined as DL physical signals. An RS, also called a pilot signal, is a signal with a predefined special waveform known to both a gNode B (gNB) and a user equipment (UE). For example, cell specific RS, UE-specific RS (UE-RS), positioning RS (PRS), and channel state information RS (CSI-RS) are defined as DL RSs. The 3GPP LTE/LTE-A standards define uplink (UL) physical channels corresponding to REs carrying information originated from a higher layer, and UL physical signals which are used in the physical layer and correspond to REs which do not carry information originated from a higher layer. For example, physical uplink shared channel (PUSCH), physical uplink control channel (PUCCH), and physical random access channel (PRACH) are defined as UL physical channels, and a demodulation reference signal (DMRS) for a UL control/data signal, and a sounding reference signal (SRS) used for UL channel measurement are defined as UL physical signals.

In the present disclosure, the PDCCH/PCFICH/PHICH/PDSCH refers to a set of time-frequency resources or a set of REs, which carry downlink control information (DCI)/a control format indicator (CFI)/a DL acknowledgement/negative acknowledgement (ACK/NACK)/DL data. Further, the PUCCH/PUSCH/PRACH refers to a set of time-frequency resources or a set of REs, which carry UL control information (UCI)/UL data/a random access signal. In the present disclosure, particularly a time-frequency resource or an RE which is allocated to or belongs to the PDCCH/PCFICH/PHICH/PDSCH/PUCCH/PUSCH/PRACH is referred to as a PDCCH RE/PCFICH RE/PHICH RE/PDSCH RE/PUCCH RE/PUSCH RE/PRACH RE or a PDCCH resource/PCFICH resource/PHICH resource/PDSCH resource/PUCCH resource/PUSCH resource/PRACH resource. Hereinbelow, if it is said that a UE transmits a PUCCH/PUSCH/PRACH, this means that UCI/UL data/a random access signal is transmitted on or through the PUCCH/PUSCH/PRACH. Further, if it is said that a gNB transmits a PDCCH/PCFICH/PHICH/PDSCH, this means that DCI/control information is transmitted on or through the PDCCH/PCFICH/PHICH/PDSCH.

Hereinbelow, an orthogonal frequency division multiplexing (OFDM) symbol/carrier/subcarrier/RE to which a CRS/DMRS/CSI-RS/SRS/UE-RS is allocated to or for which the CRS/DMRS/CSI-RS/SRS/UE-RS is configured is referred to as a CRS/DMRS/CSI-RS/SRS/UE-RS symbol/carrier/subcarrier/RE. For example, an OFDM symbol to which a tracking RS (TRS) is allocated or for which the TRS is configured is referred to as a TRS symbol, a subcarrier to which a TRS is allocated or for which the TRS is configured is referred to as a TRS subcarrier, and an RE to which a TRS is allocated or for which the TRS is configured is referred to as a TRS RE. Further, a subframe configured to transmit a TRS is referred to as a TRS subframe. Further, a subframe carrying a broadcast signal is referred to as a broadcast subframe or a PBCH subframe, and a subframe carrying a synchronization signal (SS) (e.g., a primary synchronization signal (PSS) and/or a secondary synchronization signal (SSS)) is referred to as an SS subframe or a PSS/SSS subframe. An OFDM symbol/subcarrier/RE to which a PSS/SSS is allocated or for which the PSS/SSS is configured is referred to as a PSS/SSS symbol/subcarrier/RE.

In the present disclosure, a CRS port, a UE-RS port, a CSI-RS port, and a TRS port refer to an antenna port configured to transmit a CRS, an antenna port configured to transmit a UE-RS, an antenna port configured to transmit a CSI-RS, and an antenna port configured to transmit a TRS, respectively. Antenna port configured to transmit CRSs may be distinguished from each other by the positions of REs occupied by the CRSs according to CRS ports, antenna ports configured to transmit UE-RSs may be distinguished from each other by the positions of REs occupied by the UE-RSs according to UE-RS ports, and antenna ports configured to transmit CSI-RSs may be distinguished from each other by the positions of REs occupied by the CSI-RSs according to CSI-RS ports. Therefore, the term CRS/UE-RS/CSI-RS/TRS port is also used to refer to a pattern of REs occupied by a CRS/UE-RS/CSI-RS/TRS in a predetermined resource area.

FIG. 1 illustrates wireless devices applicable to the present disclosure.

Referring to FIG. 1, a first wireless device 100 and a second wireless device 200 may transmit wireless signals through a variety of RATs (e.g., LTE and NR). {The first wireless device 100 and the second wireless device 200} may correspond to {the wireless device 100 x and the BS 200} and/or {the wireless device 100 x and the wireless device 100 x} of FIG. 34.

The first wireless device 100 may include one or more processors 102 and one or more memories 104, and further include one or more transceivers 106 and/or one or more antennas 108. The processor(s) 102 may control the memory(s) 104 and/or the transceiver(s) 106 and may be configured to implement the descriptions, functions, procedures, proposals, methods, and/or operation flowcharts disclosed in this document. For example, the processor(s) 102 may process information in the memory(s) 104 to generate first information/signals and then transmit wireless signals including the first information/signals through the transceiver(s) 106. The processor(s) 102 may receive wireless signals including second information/signals through the transceiver(s) 106 and then store information obtained by processing the second information/signals in the memory(s) 104. The memory(s) 104 may be connected to the processor(s) 102 and may store various pieces of information related to operations of the processor(s) 102. For example, the memory(s) 104 may store software code including instructions for performing all or a part of processes controlled by the processor(s) 102 or for performing the descriptions, functions, procedures, proposals, methods, and/or operation flowcharts disclosed in this document. The processor(s) 102 and the memory(s) 104 may be a part of a communication modem/circuit/chip designed to implement RAT (e.g., LTE or NR). The transceiver(s) 106 may be connected to the processor(s) 102 and transmit and/or receive wireless signals through the one or more antennas 108. Each of the transceiver(s) 106 may include a transmitter and/or a receiver. The transceiver(s) 106 may be interchangeably used with radio frequency (RF) unit(s). In the present disclosure, the wireless device may be a communication modem/circuit/chip.

Hereinafter, a description will be given of instructions and/or operations controlled by the processor(s) 102 and stored in the memory(s) 104 of the first wireless device 100 according to an embodiment of the present disclosure.

While the following operations are described in the context of control operations of the processor(s) 102 from the perspective of the processor(s) 102, software code for performing the operations may be stored in the memory(s) 104.

The processor(s) 102 may be configured to control the transceiver(s) 106 to receive information on an actual transmitted SS/PBCH block that is actually transmitted among a plurality of SS/PBCH blocks. The processor(s) 102 may be configured to control the transceiver(s) 106 to receive an SS/PBCH block based on the ATSS information and obtain information about the transmission timing of the SS/PBCH block based on the PBCH payload of the SS/PBCH block, a PBCH DMRS, and/or the phase of the SS/PBCH block. Particularly, the processor(s) 102 may operate according to the following embodiments.

Hereinafter, a description will be given of instructions and/or operations controlled by processor(s) 202 and stored in memory(s) 204 of the second wireless device 200 according to an embodiment of the present disclosure.

While the following operations are described in the context of control operations of the processor(s) 202 from the perspective of the processor(s) 202, software code for performing the operations may be stored in the memory(s) 204.

The processor(s) 202 may be configured to control transceiver(s) 206 to transmit information on an ATSS that is actually transmitted among a plurality of SS/PBCH blocks to the first wireless device 100. The processor(s) 202 may be configured to perform a CAP for transmitting an SS/PBCH block in an unlicensed band. If the CAP is successful, the processor(s) 202 may be configured to control the transceiver(s) 206 to generate and transmit the SS/PBCH block based on the transmission timing of the SS/PBCH block and the ATSS information. Particularly, the processor(s) 202 may operate according to the following embodiments.

Now, hardware elements of the wireless devices 100 and 200 will be described in greater detail. One or more protocol layers may be implemented by, not limited to, one or more processors 102 and 202. For example, the one or more processors 102 and 202 may implement one or more layers (e.g., functional layers such as physical (PHY), medium access control (MAC), radio link control (RLC), packet data convergence protocol (PDCP), RRC, and service data adaptation protocol (SDAP)). The one or more processors 102 and 202 may generate one or more protocol data units (PDUs) and/or one or more service data Units (SDUs) according to the descriptions, functions, procedures, proposals, methods, and/or operation flowcharts disclosed in this document. The one or more processors 102 and 202 may generate messages, control information, data, or information according to the descriptions, functions, procedures, proposals, methods, and/or operation flowcharts disclosed in this document and provide the messages, control information, data, or information to one or more transceivers 106 and 206. The one or more processors 102 and 202 may generate signals (e.g., baseband signals) including PDUs, SDUs, messages, control information, data, or information according to the descriptions, functions, procedures, proposals, methods, and/or operation flowcharts disclosed in this document and provide the generated signals to the one or more transceivers 106 and 206. The one or more processors 102 and 202 may receive the signals (e.g., baseband signals) from the one or more transceivers 106 and 206 and acquire the PDUs, SDUs, messages, control information, data, or information according to the descriptions, functions, procedures, proposals, methods, and/or operation flowcharts disclosed in this document.

The one or more processors 102 and 202 may be referred to as controllers, microcontrollers, microprocessors, or microcomputers. The one or more processors 102 and 202 may be implemented by hardware, firmware, software, or a combination thereof. For example, one or more application specific integrated circuits (ASICs), one or more digital signal processors (DSPs), one or more digital signal processing devices (DSPDs), one or more programmable logic devices (PLDs), or one or more field programmable gate arrays (FPGAs) may be included in the one or more processors 102 and 202. The descriptions, functions, procedures, proposals, methods, and/or operation flowcharts disclosed in this document may be implemented using firmware or software, and the firmware or software may be configured to include the modules, procedures, or functions. Firmware or software configured to perform the descriptions, functions, procedures, proposals, methods, and/or operation flowcharts disclosed in this document may be included in the one or more processors 102 and 202 or may be stored in the one or more memories 104 and 204 and executed by the one or more processors 102 and 202. The descriptions, functions, procedures, proposals, methods, and/or operation flowcharts disclosed in this document may be implemented using firmware or software in the form of code, an instruction, and/or a set of instructions.

The one or more memories 104 and 204 may be connected to the one or more processors 102 and 202 and store various types of data, signals, messages, information, programs, code, instructions, and/or commands. The one or more memories 104 and 204 may be configured to include read-only memories (ROMs), random access memories (RAMs), electrically erasable programmable read-only memories (EPROMs), flash memories, hard drives, registers, cash memories, computer-readable storage media, and/or combinations thereof. The one or more memories 104 and 204 may be located at the interior and/or exterior of the one or more processors 102 and 202. The one or more memories 104 and 204 may be connected to the one or more processors 102 and 202 through various technologies such as wired or wireless connection.

The one or more transceivers 106 and 206 may transmit user data, control information, and/or wireless signals/channels, mentioned in the methods and/or operation flowcharts of this document, to one or more other devices. The one or more transceivers 106 and 206 may receive user data, control information, and/or wireless signals/channels, mentioned in the descriptions, functions, procedures, proposals, methods, and/or operation flowcharts disclosed in this document, from one or more other devices. For example, the one or more transceivers 106 and 206 may be connected to the one or more processors 102 and 202 and transmit and receive wireless signals. For example, the one or more processors 102 and 202 may perform control so that the one or more transceivers 106 and 206 may transmit user data, control information, or wireless signals to one or more other devices. The one or more processors 102 and 202 may perform control so that the one or more transceivers 106 and 206 may receive user data, control information, or wireless signals from one or more other devices. The one or more transceivers 106 and 206 may be connected to the one or more antennas 108 and 208 and the one or more transceivers 106 and 206 may be configured to transmit and receive user data, control information, and/or wireless signals/channels, mentioned in the descriptions, functions, procedures, proposals, methods, and/or operation flowcharts disclosed in this document, through the one or more antennas 108 and 208. In this document, the one or more antennas may be a plurality of physical antennas or a plurality of logical antennas (e.g., antenna ports). The one or more transceivers 106 and 206 may convert received wireless signals/channels from RF band signals into baseband signals in order to process received user data, control information, and wireless signals/channels using the one or more processors 102 and 202. The one or more transceivers 106 and 206 may convert the user data, control information, and wireless signals/channels processed using the one or more processors 102 and 202 from the baseband signals into the RF band signals. To this end, the one or more transceivers 106 and 206 may include (analog) oscillators and/or filters.

FIG. 2 illustrates another example of a wireless device applied to the present disclosure. The wireless device may be implemented in various forms according to a use case/service (refer to FIG. 34).

Referring to FIG. 2, wireless devices 100 and 200 may correspond to the wireless devices 100 and 200 of FIG. 23 and may be configured to include various elements, components, units/portions, and/or modules. For example, each of the wireless devices 100 and 200 may include a communication unit 110, a control unit 120, a memory unit 130, and additional components 140. The communication unit 110 may include a communication circuit 112 and transceiver(s) 114. For example, the communication circuit 112 may include the one or more processors 102 and 202 and/or the one or more memories 104 and 204 of FIG. 23. For example, the transceiver(s) 114 may include the one or more transceivers 106 and 206 and/or the one or more antennas 108 and 208 of FIG. 29. The control unit 120 is electrically connected to the communication unit 110, the memory 130, and the additional components 140 and provides overall control to the wireless device. For example, the control unit 120 may control an electric/mechanical operation of the wireless device based on programs/code/instructions/information stored in the memory unit 130. The control unit 120 may transmit the information stored in the memory unit 130 to the outside (e.g., other communication devices) via the communication unit 110 through a wireless/wired interface or store, in the memory unit 130, information received through the wireless/wired interface from the outside (e.g., other communication devices) via the communication unit 110.

The additional components 140 may be configured in various manners according to type of the wireless device. For example, the additional components 140 may include at least one of a power unit/battery, input/output (I/O) unit, a driving unit, and a computing unit. The wireless device may be implemented in the form of, not limited to, the robot (100 a of FIG. 34), the vehicles (100 b-1 and 100 b-2 of FIG. 34), the XR device (100 c of FIG. 34), the hand-held device (100 d of FIG. 34), the home appliance (100 e of FIG. 34), the IoT device (100 f of FIG. 34), a digital broadcasting terminal, a hologram device, a public safety device, an MTC device, a medical device, a FinTech device (or a finance device), a security device, a climate/environment device, the AI server/device (400 of FIG. 34), the BSs (200 of FIG. 34), a network node, or the like. The wireless device may be mobile or fixed according to a use case/service.

In FIG. 2, all of the various elements, components, units/portions, and/or modules in the wireless devices 100 and 200 may be connected to each other through a wired interface or at least a part thereof may be wirelessly connected through the communication unit 110. For example, in each of the wireless devices 100 and 200, the control unit 120 and the communication unit 110 may be connected by wire and the control unit 120 and first units (e.g., 130 and 140) may be wirelessly connected through the communication unit 110. Each element, component, unit/portion, and/or module in the wireless devices 100 and 200 may further include one or more elements. For example, the control unit 120 may be configured with a set of one or more processors. For example, the control unit 120 may be configured with a set of a communication control processor, an application processor, an electronic control unit (ECU), a graphical processing unit, and a memory control processor. In another example, the memory 130 may be configured with a RAM, a dynamic RAM (DRAM), a ROM, a flash memory, a volatile memory, a non-volatile memory, and/or a combination thereof.

The implementation example of FIG. 2 will hereinafter be described with reference to the attached drawings.

FIG. 3 is a block diagram illustrating a hand-held device 100 to which another embodiment of the present disclosure can be applied. The hand-held device may include a smartphone, a tablet (also called a smartpad), a wearable device (e.g., a smartwatch or smart glasses), and a portable computer (e.g., a laptop). The hand-held device 100 may be referred to as a mobile station (MS), a user terminal (UT), a mobile subscriber station (MSS), a subscriber station (SS), an advanced mobile station (AMS), or a wireless terminal (WT).

Referring to FIG. 3, the hand-held device 100 may include an antenna unit 108, a communication unit 110, a control unit 120, a memory unit 130, a power supply unit 140 a, an interface unit 140 b, and an input/output (I/O) unit 140 c. The antenna unit 108 may be configured as a part of the communication unit 110. The blocks 110 to 130/140 a to 140 c correspond to the blocks 110 to 130/140 of FIG. 2, respectively.

The communication unit 110 may transmit and receive signals (e.g., data and control signals) to and from another wireless device and a BS. The control unit 120 may perform various operations by controlling elements of the hand-held device 100. The control unit 120 may include an application processor (AP). The memory unit 130 may store data/parameters/programs/code/commands required for operation of the hand-held device 100. Further, the memory unit 130 may store input/output data/information. The power supply unit 140 a may supply power to the hand-held device 100, and include a wired/wireless charging circuit and a battery. The interface unit 140 b may support connection between the hand-held device and other external devices. The interface unit 140 b may include various ports (e.g., an audio I/O port and a video I/O port) for connection to external devices. The I/O unit 140 c may receive or output video information/signal, audio information/signal, data, and/or user-input information. The I/O unit 140 c may include a camera, a microphone, a user input unit, a display 140 d, a speaker, and/or a haptic module.

For example, for data communication, the I/O unit 140 c may acquire information/signals (e.g., touch, text, voice, images, and video) received from the user and store the acquired information/signals in the memory unit 130. The communication unit 110 may convert the information/signals into radio signals and transmit the radio signals directly to another device or to a BS. Further, the communication unit 110 may receive a radio signal from another device or a B S and then restore the received radio signal to original information/signal. The restored information/signal may be stored in the memory unit 130 and output in various forms (e.g., text, voice, an image, video, and a haptic effect) through the I/O unit 140 c.

FIG. 4 illustrates a vehicle or an autonomous driving vehicle applied to the present disclosure. The vehicle or autonomous driving vehicle may be implemented as a mobile robot, a car, a train, a manned/unmanned aerial vehicle (AV), a ship, or the like.

Referring to FIG. 4, a vehicle or autonomous driving vehicle 100 may include an antenna unit 108, a communication unit 110, a control unit 120, a driving unit 140 a, a power supply unit 140 b, a sensor unit 140 c, and an autonomous driving unit 140 d. The antenna unit 108 may be configured as a part of the communication unit 110. The blocks 110/130/140 a to 140 d correspond to the blocks 110/130/140 of FIG. 2, respectively.

The communication unit 110 may transmit and receive signals (e.g., data and control signals) to and from external devices such as other vehicles, BSs (e.g., gNBs and road side units), and servers. The control unit 120 may perform various operations by controlling elements of the vehicle or the autonomous driving vehicle 100. The control unit 120 may include an ECU. The driving unit 140 a may enable the vehicle or the autonomous driving vehicle 100 to drive on a road. The driving unit 140 a may include an engine, a motor, a powertrain, a wheel, a brake, a steering device, and so on. The power supply unit 140 b may supply power to the vehicle or the autonomous driving vehicle 100 and include a wired/wireless charging circuit, a battery, and so on. The sensor unit 140 c may acquire information about a vehicle state, ambient environment information, user information, and so on. The sensor unit 140 c may include an inertial measurement unit (IMU) sensor, a collision sensor, a wheel sensor, a speed sensor, a slope sensor, a weight sensor, a heading sensor, a position module, a vehicle forward/backward sensor, a battery sensor, a fuel sensor, a tire sensor, a steering sensor, a temperature sensor, a humidity sensor, an ultrasonic sensor, an illumination sensor, a pedal position sensor, and so on. The autonomous driving unit 140 d may implement technology for maintaining a lane on which the vehicle is driving, technology for automatically adjusting speed, such as adaptive cruise control, technology for autonomously driving along a determined path, technology for driving by automatically setting a route if a destination is set, and the like.

For example, the communication unit 110 may receive map data, traffic information data, and so on from an external server. The autonomous driving unit 140 d may generate an autonomous driving route and a driving plan from the obtained data. The control unit 120 may control the driving unit 140 a such that the vehicle or autonomous driving vehicle 100 may move along the autonomous driving route according to the driving plan (e.g., speed/direction control). During autonomous driving, the communication unit 110 may aperiodically/periodically acquire recent traffic information data from the external server and acquire surrounding traffic information data from neighboring vehicles. During autonomous driving, the sensor unit 140 c may obtain information about a vehicle state and/or surrounding environment information. The autonomous driving unit 140 d may update the autonomous driving route and the driving plan based on the newly obtained data/information. The communication unit 110 may transfer information about a vehicle position, the autonomous driving route, and/or the driving plan to the external server. The external server may predict traffic information data using AI technology based on the information collected from vehicles or autonomous driving vehicles and provide the predicted traffic information data to the vehicles or the autonomous driving vehicles.

FIG. 5 illustrates a signal processing circuit for transmission (Tx) signals.

Referring to FIG. 5, a signal processing circuit 1000 may include a scrambler 1010, a modulator 1020, a layer mapper 1030, a precoder 1040, a resource mapper 1050, and a signal generator 1060. The operations/functions shown in FIG. 29 may be performed by the processors 102 and 202 and/or the transceivers 106 and 206 shown in FIG. 1, without being limited thereto. Hardware elements shown in FIG. 5 may be implemented by the processors 102 and 202 and/or the transceivers 106 and 206 shown in FIG. 1. For example, the blocks 1010 to 1060 may be implemented by the processors 102 and 202 shown in FIG. 1. In addition, the blocks 1010 to 1050 may be implemented by the processors 102 and 202 shown in FIG. 1, and the block 1060 may be implemented by the transceivers 106 and 206 shown in FIG. 1.

The codeword may be converted into a radio signal (or a radio frequency (RF) signal) through the signal processing circuit 1000 shown in FIG. 5. Here, the codeword may be a coded bit sequence of an information block. The information block may include a transmission (Tx) block (e.g., UL-SCH transmission block, and/or DL-SCH transmission block). The radio signal may be transmitted through various physical channels (e.g., PUSCH, and PDSCH).

In more detail, the codeword may be converted into a bit sequence scrambled by the scrambler 1010. The scramble sequence used for such scrambling may be generated based on an initialization value, and the initialization value may include ID information of a wireless device, etc. The scrambled bit-sequence may be modulated into a modulated symbol sequence by the demodulator 1020. The modulation scheme may include pi/2-BPSK(pi/2-Binary Phase Shift Keying), m-PSK (m-Phase Shift Keying), m-QAM (m-Quadrature Amplitude Modulation), etc. The complex modulated symbol sequence may be mapped to one or more transmission (Tx) layers by the layer mapper 1030. Modulated symbols of the respective Tx layers may be mapped (precoded) to the corresponding antenna port(s) by the precoder 1040. The output value (z) of the precoder 1040 may be obtained by multiplying the output value (y) of the layer mapper 1030 by the (N×M) precoding matrix (W). In this case, N is the number of antenna ports, and M is the number of Tx layers. In this case, the precoder 1040 may perform precoding after transform precoding (e.g., DFT transform) is performed on the complex modulated symbols. In this case, the precoder 1040 may perform precoding without performing transform precoding.

The resource mapper 1050 may map the modulated symbols of the respective antenna ports to time-frequency resources. The time-frequency resources may include a plurality of symbols (e.g., CP-OFDMA symbol and DFT-s-OFDMA symbol) in the time domain, and may include a plurality of subcarriers in the frequency domain. The signal generator 1060 may generate radio signals from the mapped modulated symbols, and the generated radio signals may be transferred to other devices through the respective antennas. To this end, the signal generator 1060 may include an inverse fast Fourier transform (IFFT) module, a cyclic prefix (CP) inserter, a digital-to-analog converter (DAC), a frequency uplink converter, etc.

The signal processing steps for reception (Rx) signals in the wireless device may be arranged in the reverse order of the signal processing steps 1010 to 1060 shown in FIG. 29. For example, the wireless devices 100 and 200 (shown in FIG. 25) may receive radio signals from the outside through the antenna ports/transceivers. The received radio signals may be converted into a baseband signal through a signal restorer. To this end, the signal restorer may include a frequency downlink converter, an analog-to-digital converter (ADC), a CP remover, and a fast Fourier transform (FFT) module. Thereafter, the baseband signal may be restored to the codeword after passing through the resource demapper process, the postcoding process, the demodulation process, and the descrambling process. The codeword may be restored to an original information block through decoding. Therefore, the signal processing circuit (not shown) for Rx signals may include a signal restorer, a resource demapper, a postcoder, a demodulator, a descrambler, and a decoder.

FIG. 6 illustrates control-plane and user-plane protocol stacks in a radio interface protocol architecture conforming to a 3GPP wireless access network standard between a UE and an evolved UMTS terrestrial radio access network (E-UTRAN). The control plane is a path in which the UE and the E-UTRAN transmit control messages to manage calls, and the user plane is a path in which data generated from an application layer, for example, voice data or Internet packet data is transmitted.

A physical (PHY) layer at layer 1 (L1) provides information transfer service to its higher layer, a medium access control (MAC) layer. The PHY layer is connected to the MAC layer via transport channels. The transport channels deliver data between the MAC layer and the PHY layer. Data is transmitted on physical channels between the PHY layers of a transmitter and a receiver. The physical channels use time and frequency as radio resources. Specifically, the physical channels are modulated in orthogonal frequency division multiple access (OFDMA) for downlink (DL) and in single carrier frequency division multiple access (SC-FDMA) for uplink (UL).

The MAC layer at layer 2 (L2) provides service to its higher layer, a radio link control (RLC) layer via logical channels. The RLC layer at L2 supports reliable data transmission. RLC functionality may be implemented in a function block of the MAC layer. A packet data convergence protocol (PDCP) layer at L2 performs header compression to reduce the amount of unnecessary control information and thus efficiently transmit Internet protocol (IP) packets such as IP version 4 (IPv4) or IP version 6 (IPv6) packets via an air interface having a narrow bandwidth.

A radio resource control (RRC) layer at the lowest part of layer 3 (or L3) is defined only on the control plane. The RRC layer controls logical channels, transport channels, and physical channels in relation to configuration, reconfiguration, and release of radio bearers. A radio bearer refers to a service provided at L2, for data transmission between the UE and the E-UTRAN. For this purpose, the RRC layers of the UE and the E-UTRAN exchange RRC messages with each other. If an RRC connection is established between the UE and the E-UTRAN, the UE is in RRC Connected mode and otherwise, the UE is in RRC Idle mode. A Non-Access Stratum (NAS) layer above the RRC layer performs functions including session management and mobility management.

DL transport channels used to deliver data from the E-UTRAN to UEs include a broadcast channel (BCH) carrying system information, a paging channel (PCH) carrying a paging message, and a shared channel (SCH) carrying user traffic or a control message. DL multicast traffic or control messages or DL broadcast traffic or control messages may be transmitted on a DL SCH or a separately defined DL multicast channel (MCH). UL transport channels used to deliver data from a UE to the E-UTRAN include a random access channel (RACH) carrying an initial control message and a UL SCH carrying user traffic or a control message. Logical channels that are defined above transport channels and mapped to the transport channels include a broadcast control channel (BCCH), a paging control channel (PCCH), a Common Control Channel (CCCH), a multicast control channel (MCCH), a multicast traffic channel (MTCH), etc.

The use of an ultra-high frequency band, that is, a millimeter frequency band at or above 6 GHz is under consideration in the NR system to transmit data in a wide frequency band, while maintaining a high transmission rate for multiple users. The 3GPP calls this system NR. In the present disclosure, the system will also be referred to as an NR system.

In the NR system, a massive multiple input multiple output (MIMO) environment in which the number of transmission/reception (Tx/Rx) antennas is significantly increased may be under consideration. That is, as the massive MIMO environment is considered, the number of Tx/Rx antennas may be increased to a few tens or hundreds. The NR system supports communication in an above 6 GHz band, that is, a millimeter frequency band. However, the millimeter frequency band is characterized by the frequency property that a signal is very rapidly attenuated according to a distance due to the use of too high a frequency band. Therefore, in an NR system operating at or above 6 GHz, beamforming (BF) is considered, in which a signal is transmitted with concentrated energy in a specific direction, not omni-directionally, to compensate for rapid propagation attenuation. Accordingly, there is a need for hybrid BF with analog BF and digital BF in combination according to a position to which a BF weight vector/precoding vector is applied, for the purpose of increased performance, flexible resource allocation, and easiness of frequency-wise beam control in the massive MIMO environment.

FIG. 7 is a block diagram illustrating an exemplary transmitter and receiver for hybrid BF.

To form a narrow beam in the millimeter frequency band, a BF method is mainly considered, in which a BS or a UE transmits the same signal through multiple antennas by applying appropriate phase differences to the antennas and thus increasing energy only in a specific direction. Such BF methods include digital BF for generating a phase difference for digital baseband signals, analog BF for generating phase differences by using time delays (i.e., cyclic shifts) for modulated analog signals, and hybrid BF with digital BF and analog beamforming in combination. Use of a radio frequency (RF) unit (or transceiver unit (TXRU)) for antenna element to control transmission power and phase control on antenna element basis enables independent BF for each frequency resource. However, installing TXRUs in all of about 100 antenna elements is less feasible in terms of cost. That is, a large number of antennas are required to compensate for rapid propagation attenuation in the millimeter frequency, and digital BF needs as many RF components (e.g., digital-to-analog converters (DACs), mixers, power amplifiers, and linear amplifiers) as the number of antennas. As a consequence, implementation of digital BF in the millimeter frequency band increases the prices of communication devices. Therefore, analog BF or hybrid BF is considered, when a large number of antennas are needed as is the case with the millimeter frequency band. In analog BF, a plurality of antenna elements are mapped to a single TXRU and a beam direction is controlled by an analog phase shifter. Because only one beam direction is generated across a total band in analog BF, frequency-selective BF may not be achieved with analog BF. Hybrid BF is an intermediate form of digital BF and analog BF, using B RF units fewer than Q antenna elements. In hybrid BF, the number of beam directions available for simultaneous transmission is limited to B or less, which depends on how B RF units and Q antenna elements are connected.

Quasi Co-Location (QCL)

A UE may receive a list including up to M transmission configuration indicator (TCI) state configurations to decode a PDSCH according to a detected PDCCH with DCI intended for the UE and a given serving cell. In this case, M depends on the capability of the UE.

Each TCI state includes a parameter for configuring a QCL relationship between one or two DL RSs and DMRS ports of the PDSCH. The QCL relationship is configured with a RRC parameter qcl-Type1 for the first DL RS and a qcl-Type2 for the second DL RS (if configured).

The QCL type related to each DL RS may be given by a parameter ‘qcl-Type’ in QCL-Info and may have one of the following values.

-   -   ‘QCL-TypeA’: {Doppler shift, Doppler spread, average delay,         delay spread}     -   ‘QCL-TypeB’: {Doppler shift, Doppler spread}     -   ‘QCL-TypeC’: {Doppler shift, average delay}     -   ‘QCL-TypeD’: {Spatial Rx parameter}

For example, when a target antenna port is a specific non-zero power (NZP) CSI-RS, it may be indicated/configured that related NZP CSI-RS antenna ports are quasi co-located (QCLed) with a specific TRS in terms of QCL-Type A and QCLed with a specific SSB in terms of QCL-Type D. Upon receiving the above indication/configuration, the UE may receive the corresponding NZP CSI-RS based on Doppler and delay values measured for the QCL-TypeA TRS. In this case, the UE may apply a reception beam used to receive the QCL-TypeD SSB to the reception of the corresponding NZP CSI-RS.

Downlink Beam Management (DL BM)

The BM refers to a series of processes for acquiring and maintaining a set of BS beams (transmission and reception point (TRP) beams) and/or a set of UE beams available for DL and UL transmission/reception. The BM may include the following processes and terminology.

-   -   Beam measurement: an operation by which the BS or UE measures         the characteristics of a received beamformed signal     -   Beam determination: an operation by which the BS or UE selects         its Tx/Rx beams     -   Beam sweeping: an operation of covering a spatial domain by         using Tx and/or Rx beams for a prescribed time interval         according to a predetermined method     -   Beam report: an operation by which the UE reports information         about a signal beamformed based on the beam measurement.

The BM process may be divided into (1) a DL BM process based on an SSB or CSI-RS, and (2) a UL BM process based on an SRS. Each BM process may include Tx beam sweeping for determining TX beams and Rx beam sweeping for determining Rx beams.

The DL BM process may include (1) transmission of DL RSs (e.g., CSI-RSs or SSBs) beamformed by the BS and (2) beam reporting by the UE.

Beam reporting may include preferred DL RS ID(s) and reference signal received power (RSRP) related thereto. The DL RS ID may be a SSB resource indicator (SSBRI) or a CSI-RS resource indicator (CRI).

FIG. 8 illustrates an example of beamforming based on an SSB and a CSI-RS.

As shown in FIG. 8, an SSB beam and a CSI-RS beam may be used for beam measurement. The measurement metric is RSRP for each resource/block. The SSB may be used for coarse beam measurement, and the CSI-RS may be used for fine beam measurement. The SSB may be used for both Tx beam sweeping and Rx beam sweeping. The Rx beam sweeping based on the SSB may be performed as follows: the UE may attempt receive SSBs while changing Rx beams for the same SSBRI across multiple SSB bursts. Here, one SS burst includes one or more SSBs, and one SS burst set may include one or more SSB bursts.

1. DL BM Based on SSB

FIG. 9 is a flowchart illustrating an exemplary DL BM process based on an SSB.

The configuration of beam reporting based on the SSB may be performed when CSI/beams are configured in the RRC_CONNECTED state.

-   -   The UE receives a CSI-ResourceConfig IE including         CSI-SSB-ResourceSetList for SSB resources used for BM from the         BS (S1110). The RRC parameter csi-SSB-ResourceSetList indicates         a list of SSB resources used for beam management and reporting         in one resource set. In this case, the SSB resource set may be         set to {SSBx1, SSBx2, SSBx3, SSBx4, . . . }, and SSB indices may         be defined from 0 to 63.     -   The UE receives signals on the SSB resources from the BS based         on the CSI-SSB-ResourceSetList (S1120).     -   When CSI-RS reportConfig related to SSBRI and RSRP reporting is         configured, the UE reports the best SSBRI and RSRP related         thereto to the BS (S1130). For example, if reportQuantity of the         CSI-RS reportConfig IE is set to ‘ssb-Index-RSRP’, the UE         reports the best SSBRI and RSRP related thereto to the BS.

If the UE is configured with a CSI-RS resource in in the same OFDM symbol(s) as the SSB and if ‘QCL-TypeD’ is applicable, the UE may assume that the CSI-RS and the SSB are QCLed in terms of ‘QCL-TypeD’. Here, QCL-TypeD may mean that antenna ports are QCLed in terms of spatial Rx parameters. When the UE receives signals on a plurality of DL antenna ports in the QCL-TypeD relationship, the UE may apply the same Rx beam.

2. DL BM Based on CSI-RS

The CSI-RS may be used for the following purposes: for a specific CSI-RS resource set, i) if a repetition parameter is configured and TRS info is not configured, the CSI-RS is used for BM; ii) if no repetition parameter is configured and TRS info is configured, the CSI-RS is used as a tracking reference signal (TRS); and/or iii) if no repetition parameter is configured and TRS info is not configured, the CSI-RS is used for CSI acquisition.

When the (RRC parameter) repetition is set to ‘ON’, it may be related to the Rx beam sweeping process of the UE. When the repetition is set to ‘ON’, if the UE is configured with NZP-CSI-RS-ResourceSet, the UE may assume that signals on one or more CSI-RS resources in NZP-CSI-RS-ResourceSet are transmitted through the same DL spatial domain filter. That is, the one or more CSI-RS resources in NZP-CSI-RS-ResourceSet may be transmitted on the same Tx beam. In this case, the signals on the one or more CSI-RS resources in NZP-CSI-RS-ResourceSet may be transmitted in different OFDM symbols.

On the other hand, when the repetition is set to ‘OFF’, it may be related to the Tx beam sweeping process of the BS. When the repetition is set to ‘OFF’, the UE does not assume that signals on one or more CSI-RS resources in NZP-CSI-RS-ResourceSet are transmitted through the same DL spatial domain transmission filter. That is, the signals on the one or more CSI-RS resources in NZP-CSI-RS-ResourceSet may be transmitted through different Tx beams. FIG. 12 illustrates another example of a DL BM process based on a CSI-RS.

FIG. 10(a) illustrates an RX beam determination (or refinement) process of the UE, and FIG. 10(b) illustrates a Tx beam sweeping process of the BS. Specifically, FIG. 10(a) shows a case where the repetition parameter is set to ‘ON’, and FIG. 10(b) shows a case where the repetition parameter is set to ‘OFF’.

The Rx beam determination process of the UE will be described with reference to FIGS. 10(a) and 11(a).

FIG. 11(a) is a flowchart illustrating the Rx beam determination process of the UE.

-   -   The UE receives a NZP CSI-RS resource set IE including the RRC         parameter for ‘repetition’ from the BS through RRC signaling         (S1110). In this case, the RRC parameter ‘repetition’ is set to         ‘ON’.     -   The UE receives signals on resource(s) in the CSI-RS resource         set in which the RRC parameter ‘repetition’ is set to ‘ON’         through the same Tx beam (or DL spatial domain transmission         filter) of the BS in different OFDM symbols (S1120).     -   The UE determines its Rx beam (S1130).     -   The UE does not perform CSI reporting (S1140). That is, when the         RRC parameter ‘repetition’ is set to ‘ON’, the UE may skip the         CSI reporting.

The Tx beam determination process of the BS will be described with reference to FIGS. 10(b) and 11(b).

FIG. 11(b) is a flowchart illustrating the Tx beam determination process of the BS.

-   -   The UE receives a NZP CSI-RS resource set IE including the RRC         parameter for ‘repetition’ from the BS through RRC signaling         (S1150). In this case, the RRC parameter ‘repetition’ is set to         ‘OFF’ and is related to the Tx beam sweeping process of the BS.     -   The UE receives signals on resources in the CSI-RS resource set         in which the RRC parameter ‘repetition’ is set to ‘OFF’ through         different Tx beams (DL spatial domain transmission filters) of         the BS (S1160).     -   The UE selects (or determines) the best beam (S1170).     -   The UE reports the ID (e.g., CRI) of the selected beam and         quality information related thereto (e.g., RSRP) to the BS         (S1180). That is, when a CSI-RS is transmitted for BM, the UE         reports the CRI and RSRP to the BS.

FIG. 12 illustrates an example of resource allocation in the time and frequency domains in relation to the operation of FIG. 10.

When the repetition is set to ‘ON’ for a CSI-RS resource set, the same Tx beam is applied to a plurality of CSI-RS resources. When the repetition is set to ‘OFF’ for the CSI-RS resource set, different CSI-RS resources may be transmitted on different Tx beams.

3. DL BM-Related Beam Indication

The UE may receive a list of up to M candidate TCI states for QCL indication through RRC signaling. Here, M depends on the UE (capability). For example, M may be 64.

Each TCI state may be related to one RS set. Table 1 shows an example of a TCI-State IE. The TCI-State IE is related to a QCL type related to one or two DL RSs.

TABLE 1    -- ASN1START  -- TAG-TCI-STATE-START  TCI-State ::=  SEQUENCE {   tci-StateId    TCI-StateId,   qcl-Type1   QCL-Info,   qcl-Type2   QCL-Info   ...  }  QCL-Info ::= SEQUENCE {   cell   ServCellIndex   bwp-Id   BWP-Id   referenceSignal    CHOICE {    csi-rs    NZP-CSI-RS-ResourceId,    ssb    SSB-Index   },   qcl-Type   ENUMERATED {typeA, typeB, typeC, typeD},   ...  }  -- TAG-TCI-STATE-STOP  -- ASN1STOP

In Table 1, ‘bwp-Id’ denotes a DL BWP where the RS is located, ‘cell’ denotes a carrier where the RS is located, and ‘referencesignal’ denotes reference antenna port(s) corresponding to sources to be QCLed with target antenna port(s) or a reference signal including the same. Here, the target antenna port(s) may be a CSI-RS, a PDCCH DMRS, or a PDSCH DMRS.

4. Quasi Co-Location (QCL)

The UE may receive a list including up to M TCI state configurations to decode a PDSCH according to a detected PDCCH with DCI intended for the UE and a given serving cell. In this case, M depends on the capability of the UE.

As shown in Table 1, each TCI state includes a parameter for configuring a QCL relationship between one or two DL RSs and DMRS ports of the PDSCH. The QCL relationship is configured with a RRC parameter qcl-Type1 for the first DL RS and a qcl-Type2 for the second DL RS (if configured).

The QCL type related to each DL RS may be given by a parameter ‘qcl-Type’ in QCL-Info and may have one of the following values.

-   -   ‘QCL-TypeA’: {Doppler shift, Doppler spread, average delay,         delay spread}     -   ‘QCL-TypeB’: {Doppler shift, Doppler spread}     -   ‘QCL-TypeC’: {Doppler shift, average delay}     -   ‘QCL-TypeD’: {Spatial Rx parameter}

For example, when a target antenna port is a specific NZP-CSI-RS, it may be indicated/configured that related NZP CSI-RS antenna ports are QCLed with a specific TRS in terms of QCL-Type A and QCLed with a specific SSB in terms of QCL-Type D. Upon receiving the above indication/configuration, the UE may receive the corresponding NZP CSI-RS based on Doppler and delay values measured for the QCL-TypeA TRS. In this case, the UE may apply a reception beam used to receive the QCL-TypeD SSB to the reception of the corresponding NZP CSI-RS.

Beam Failure Recovery (BFR) Process

In beamformed systems, radio link failure (RLF) may frequently occur due to the rotation, movement or beamforming blockage of a UE. Accordingly, NR supports BFR to prevent the frequent occurrence of the RLF. The BFR is similar to a radio link failure recovery procedure and may be supported when the UE knows new candidate beams.

For beam failure detection, the BS may configure beam failure detection RSs for the UE, and the UE may declare beam failure when the number of beam failure indications from the physical layer of the UE reaches a threshold configured by RRC signaling from the BS within a period configured by the corresponding RRC signaling.

After detecting the beam failure, the UE may trigger beam failure recovery by initiating a random access procedure on a PCell and perform the beam failure recovery by selecting a suitable beam (if the BS provides random access resources dedicated to certain beams, the UE prioritizes the resources). When the random access procedure is completed, the beam failure recovery may be regarded to be completed.

Radio Resource Management (RRM) Measurement

Wireless communication systems support RRM operation including power control, scheduling, cell search, cell reselection, handover, radio link or connection monitoring, and connection establishment and re-establishment. In this case, a serving cell may request a UE to send RRM measurement information corresponding to a measurement value for performing the RRM operation. In particular, the UE may measure and report cell search information, reference signal received power (RSRP), reference signal received quality (RSRQ), and so on for each cell. Specifically, the UE may receive ‘measConfig’ for RRM measurement from the serving cell through higher layer signaling and then measure the RSRP or RSRQ based on information in ‘measConfig’. The definitions of the RSRP, RSRQ, and RSSI in the NR system are defined as follows in TS 38.215.

-   -   RSRP: RSRP is defined as the linear average over the power         contributions ([W]) of the resource elements (REs) for         cell-specific reference signals (CRSs) or channel state         information reference signals (CSI-RSs) transmitted in a         measurement frequency bandwidth. In NR, the RSRP may be defined         as the linear average over the power contributions ([W]) of the         REs for secondary synchronization signals (SSSs).

For RSRP determination, CRS R0 according TS 36.211 may be used. In some cases, CRS R1 may be additionally used to improve reliability. The reference point for the RSRP should be an antenna connector of a UE. If receiver diversity is in use, a reported RSRP value shall not be lower than the RSRP of anyone of individual diversities.

-   -   RSRQ: RSRQ is defined as (N*RSRP)/(E-UTRA/NR carrier RSSI or         CSI-RSSI), where N is the number of RBs in a E-UTRA/NR carrier         RSSI measurement bandwidth or a CSI-RSSI measurement bandwidth.         In this case, the measurement of ‘N*RSRP’ and the measurement of         ‘E-UTRA carrier RSSI or CSI-RSSI’ may be made over the same RB         set.     -   RSSI: RSSI means received wide band power including noise and         thermal noise generated within a bandwidth defined by a receiver         pulse shaping filter. Even in this case, the reference point for         the RSSI should be an antenna connector of a UE. If receiver         diversity is in use, a reported RSSI value shall not be lower         than the RSSI of anyone of individual diversities.

FIG. 13 illustrates a wireless communication system supporting an unlicensed band applicable to the present disclosure.

Herein, a cell operating in a licensed band (L-band) is defined as an L-cell, and a carrier in the L-cell is defined as a (DL/UL) LCC. A cell operating in an unlicensed band (U-band) is defined as a U-cell, and a carrier in the U-cell is defined as a (DL/UL) UCC. The carrier/carrier-frequency of a cell may refer to the operating frequency (e.g., center frequency) of the cell. A cell/carrier (e.g., CC) is commonly called a cell.

When a BS and a UE transmit and receive signals on an LCC and a UCC where carrier aggregation is applied as shown in FIG. 13 (a), the LCC and the UCC may be set to a primary CC (PCC) and a secondary CC (SCC), respectively. The BS and the UE may transmit and receive signals on one UCC or on a plurality of UCCs where carrier aggregation is applied as shown in FIG. 13 (b). In other words, the BS and UE may transmit and receive signals on UCC(s) with no LCC.

Signal transmission and reception operations in U-bands, which will be described later in the present disclosure, may be applied to all of the aforementioned deployment scenarios (unless specified otherwise).

The NR frame structure shown in FIG. 3 may be used for operation in a U-band. The configuration of OFDM symbols reserved for UL/DL signal transmission in a frame structure for the U-band may be determined by the BS. In this case, the OFDM symbol may be replaced with an SC-FDM(A) symbol.

For DL signal transmission in the U-band, the BS may inform the UE of the configuration of OFDM symbols used in subframe #n through signaling. Herein, a subframe may be replaced with a slot or a time unit (TU).

Specifically, in the LTE system supporting U-bands, the UE may assume (or recognize) the configuration of occupied OFDM symbols in subframe #n based on a specific filed in DCI (e.g., ‘Subframe configuration for LAA’ field, etc.), which is received in subframe #n−1 or subframe #n from the BS.

Table 4 shows how the ‘Subframe configuration for LAA’ field indicates the configuration of OFDM symbols used to transmit DL physical channels and/or physical signals in the current and/or next subframe.

TABLE 2 Value of ‘Subframe Configuration of occupied configuration for LAA’ OFDM symbols (current field in current subframe subframe, next subframe) 0000 (-,14) 0001 (-,12) 0010 (-,11) 0011 (-,10) 0100 (-,9) 0101 (-,6) 0110 (-,3) 0111 (14,*) 1000 (12,-) 1001 (11,-) 1010 (10,-) 1011 (9,-) 1100 (6,-) 1101 (3,-) 1110 reserved 1111 reserved NOTE: (-, Y) means UE may assume the first Y symbols are occupied in next subframe and other symbols in the next subframe are not occupied. (X, -) means UE may assume the first X symbols are occupied in current subframe and other symbols in the current subframe are not occupied. (X, *) means UE may assume the first X symbols are occupied in current subframe, and at least the first OFDM symbol of the next subframe is not occupied.

For UL signal transmission in the U-band, the BS may provide information on a UL transmission interval to the UE through signaling.

Specifically, in the LTE system supporting U-bands, the UE may obtain ‘UL duration’ and ‘UL offset’ information on subframe #n from the ‘UL duration and offset’ field in detected DCI.

Table 3 shows how the ‘UL duration and offset’ field indicates the configurations of a UL offset and a UL duration.

TABLE 3 Value of ‘UL duration and UL offset, l(in UL duration, d(in offset’ field subframes) subframes) 00000 Not configured Not configured 00001 1 1 00010 1 2 00011 1 3 00100 1 4 00101 1 5 00110 1 6 00111 2 1 01000 2 2 01001 2 3 01010 2 4 01011 2 5 01100 2 6 01101 3 1 01110 3 2 01111 3 3 10000 3 4 10001 3 5 10010 3 6 10011 4 1 10100 4 2 10101 4 3 10110 4 4 10111 4 5 11000 4 6 11001 6 1 11010 6 2 11011 6 3 11100 6 4 11101 6 5 11110 6 6 11111 reserved reserved

For example, when the ‘UL duration and offset’ field configures (or indicates) UL offset 1 and UL duration d for subframe #n, the UE may not need to receive DL physical channels and/or physical signals in subframe #n+l+i (where i=0, 1, . . . , d−1).

The BS may perform one of the following unlicensed band access procedures (e.g., channel access procedures (CAPs)), for a DL signal transmission in an unlicensed band.

(1) First DL CAP Method

FIG. 14 is a flowchart illustrating a CAP for a DL signal transmission in an unlicensed band at a BS.

For a DL signal transmission (e.g., transmission of a signal including a PDSCH/PDCCH/EPDCCH) in an unlicensed band, a BS may initiate a CAP (S1110). The BS may randomly select a backoff counter N within a contention window (CW) according to step 1. N is set to an initial value, N_(init) (S1120). N_(init) is a random value selected from among the values between 0 and CW_(p). Subsequently, if the backoff counter N is 0 in step 4 (Y in S1130), the BS terminates the CAP (S1132). Subsequently, the BS may transmit a Tx burst including a PDSCH/PDCCH/EPDCCH (S1134). On the other hand, if the backoff counter N is not 0 (N in S1130), the BS decrements the backoff counter N by 1 according to step 2 (S1140). Subsequently, the BS determines whether a channel of U-cell(s) is in an idle state (S1150). If the channel is in the idle state (Y in S1150), the BS determines whether the backoff counter N is 0 (S1130). On the contrary, if the channel is not idle in step S1150, that is, the channel is busy (N in S1150), the BS determines whether the channel is in the idle state for a defer duration Td (25 usec or more) longer than a slot time (e.g., 9 usec) according to step 5 (S1160). If the channel is idle for the defer duration (Y in S1170), the BS may resume the CAP. The defer duration may span a period of 16 usec and the following m_(p) consecutive slot durations (e.g., 9 usec). On the contrary, if the channel is idle for the defer duration (N in S1170), the BSS re-performs step S1160 to check again whether the channel of the U-cell(s) is idle for a new defer duration.

Table 4 illustrates that m_(p), a minimum CW, a maximum CW, a maximum channel occupancy time (MCOT), and an allowed CW size for a CAP vary according to a channel access priority class.

TABLE 4 Channel Access Priority Class (p) m_(p) CW_(min, p) CW_(max, p) T_(ultcot,p) Allowed CW_(p) sizes 1 1 3 7 2 ms {3, 7}  2 1 7 15 3 ms {7, 15} 3 3 15 63 8 or 10 {15, 31, 63} ms 4 7 15 1023 8 or 10 {15, 31, 63, 127, ms 255, 511, 1023}

A CW size applied to the first DL CAP may be determined in various ways. For example, the CW size may be adjusted based on the probability of HARQ-ACK values corresponding to PDSCH transmission(s) within a predetermined time period (e.g., a reference TU) being determined to be NACK. In the case where the BS transmits a DL signal including a PDSCH related to a channel access priority class p on a carrier, when the probability of HARQ-ACK values corresponding to PDSCH transmission(s) in a reference subframe k (or a reference slot k) is 80% (z=80%), the BS increments a CW value set for each priority class to the next higher value. Alternatively, the BS maintains the CW value set for each priority class to be an initial value. The reference subframe (or reference slot) may be defined as the starting subframe (or starting slot) of the latest transmission on the carrier, for which at least some HARQ-ACK feedback is available.

(2) Second DL CAP Method

The BS may perform a DL signal transmission (e.g., a signal transmission including a discovery signal, without a PDSCH/PDCCH/EPDCCH) in an unlicensed band according to the second DL CAP method as described below.

If the signal transmission duration of the BS is 1 ms or less, the BS may perform a DL signal transmission (a signal including a discovery signal, without a PDSCH) in an unlicensed band, immediately after a corresponding channel is sensed as idle for at least a sensing interval T_(drs) (=25 us). T_(drs) includes a duration of T_(f)(=16 us) immediately followed by one slot duration T_(sl) (=9 us).

(3) Third DL CAP Method

The BS may perform the following CAPs for a DL signal transmission on multiple carriers of an unlicensed band.

1) Type A: The BS performs a CAP for multiple carriers based on a counter N (considered in the CAP) defined for each carrier, and performs a DL signal transmission based on the CAP.

-   -   Type A1: The counter N is determined independently for each         carrier, and a DL signal transmission on each carrier is         performed based on the counter N for the carrier.     -   Type A2: An N value for a carrier with the largest CW size is         determined as the counter N for each carrier, and a DL signal         transmission on each carrier is performed based on the counter N         for the carrier.

2) Type B: The BS performs a CAP based on a counter N only for a specific one of a plurality of carriers. Before a signal transmission on the specific carrier, the BS performs a DL signal transmission by determining whether the channel is idle on the other carriers.

-   -   Type B1: A single CW size is defined for a plurality of         carriers, and the BS uses the single CW size, when performing a         CAP based on a counter N for a specific carrier.     -   Type B2: A CW size is defined for each carrier, and the largest         of the CW sizes is used in determining N_(init) for a specific         carrier.

FIG. 15 illustrates an SSB structure. The UE may perform cell search, system information acquisition, beam alignment for initial access, DL measurement, and so on based on an SSB. The term SSB is used interchangeably with synchronization signal/physical broadcast channel (SS/PBCH) block.

Referring to FIG. 15, an SSB is composed of a PSS, an SSS, and a PBCH. The SSB includes four consecutive OFDM symbols. The PSS, the PBCH, the SSS/PBCH, and the PBCH are transmitted on the respective OFDM symbols. Each of the PSS and the SSS includes one OFDM symbol and 127 subcarriers, and the PBCH includes 3 OFDM symbols and 576 subcarriers. Polar coding and quadrature phase shift keying (QPSK) are applied to the PBCH. The PBCH includes data REs and demodulation reference signal (DMRS) REs in each OFDM symbol. There are three DMRS REs per RB, with three data REs between every two adjacent DMRS REs.

Cell Search

The cell search refers to a procedure in which the UE obtains time/frequency synchronization of a cell and detects a cell ID (e.g., physical layer cell ID (PCID)) of the cell. The PSS may be used in detecting a cell ID within a cell ID group, and the SSS may be used in detecting a cell ID group. The PBCH may be used in detecting an SSB (time) index and a half-frame.

The cell search procedure of the UE may be summarized as described in Table 5 below.

TABLE 5 Type of Signals Operations 1^(st) PSS * SS/PBCH block (SSB) symbol timing acquisition step * Cell ID detection within a cell ID group (3 hypothesis) 2^(nd) SSS * Cell ID group detection (336 hypothesis) Step 3^(rd) PBCH * SSB index and Half frame (HF) index (Slot and Step DMRS frame boundary detection) 4^(th) PBCH * Time information (80 ms, System Frame Number Step (SFN), SSB index, HF) * Remaining Minimum System Information (RMSI) Control resource set (CORESET)/Search space configuration 5^(th) PDCCH and * Cell access information Step PDSCH * RACH configuration

FIG. 16 illustrates SSB transmission.

Referring to FIG. 16, an SSB is periodically transmitted according to the SSB periodicity. The basic SSB periodicity assumed by the UE in the initial cell search is defined as 20 ms. After the cell access, the SSB periodicity may be set to one of {5 ms, 10 ms, 20 ms, 40 ms, 80 ms, 160 ms} by the network (e.g., the BS). An SSB burst set may be configured at the beginning of an SSB period. The SSB burst set may be configured with a 5-ms time window (i.e., half-frame), and an SSB may be repeatedly transmitted up to L times within the SS burst set. The maximum number of transmissions of the SSB, L may be given according to the frequency band of a carrier as follows. One slot includes up to two SSBs.

-   -   For frequency range up to 3 GHz, L=4     -   For frequency range from 3 GHz to 6 GHz, L=8     -   For frequency range from 6 GHz to 52.6 GHz, L=64

The time position of an SSB candidate in the SS burst set may be defined according to the SCS as follows. The time positions of SSB candidates are indexed as (SSB indexes) 0 to L−1 in temporal order within the SSB burst set (i.e., half-frame).

-   -   Case A—15-kHz SCS: The indexes of the first symbols of candidate         SSBs are given as {2, 8}+14*n where n=0, 1 for a carrier         frequency equal to or lower than 3 GHz, and n=0, 1, 2, 3 for a         carrier frequency of 3 GHz to 6 GHz.     -   Case B—30-kHz SCS: The indexes of the first symbols of candidate         SSBs are given as {4, 8, 16, 20}+28*n where n=0 for a carrier         frequency equal to or lower than 3 GHz, and n=0, 1 for a carrier         frequency of 3 GHz to 6 GHz.     -   Case C—30-kHz SCS: The indexes of the first symbols of candidate         SSBs are given as {2, 8}+14*n where n=0, 1 for a carrier         frequency equal to or lower than 3 GHz, and n=0, 1, 2, 3 for a         carrier frequency of 3 GHz to 6 GHz.     -   Case D—120-kHz SCS: The indexes of the first symbols of         candidate SSBs are given as {4, 8, 16, 20}+28*n where n=0, 1, 2,         3, 5, 6, 7, 8, 10, 11, 12, 13, 15, 16, 17, 18 fora carrier         frequency above 6 GHz.     -   Case E—240-kHz SCS: The indexes of the first symbols of         candidate SSBs are given as {8, 12, 16, 20, 32, 36, 40, 44}+56*n         where n=0, 1, 2, 3, 5, 6, 7, 8 for a carrier frequency above 6         GHz.

FIG. 17 illustrates exemplary acquisition of information about DL time synchronization at a UE.

Referring to FIG. 17, the UE may acquire DL synchronization by detecting an SSB. The UE may identify the structure of an SSB burst set based on the index of the detected SSB, and thus detect a symbol/slot/half-frame boundary. The number of a frame/half-frame to which the detected SSB belongs may be identified by SFN information and half-frame indication information.

Specifically, the UE may acquire 10-bit SFN information, s0 to s9 from a PBCH. 6 bits of the 10-bit SFN information is acquired from a master information block (MIB), and the remaining 4 bits is acquired from a PBCH transport block (TB).

Subsequently, the UE may acquire 1-bit half-frame indication information c0. If a carrier frequency is 3GH or below, the half-frame indication information may be signaled implicitly by a PBCH DMRS. The PBCH DMRS indicates 3-bit information by using one of 8 PBCH DMRS sequences. Therefore, if L=4, the remaining one bit except for two bits indicating an SSB index in the 3-bit information which may be indicated by 8 PBCH DMRS sequences may be used for half-frame indication.

Finally, the UE may acquire an SSB index based on the DMRS sequence and the PBCH payload. SSB candidates are indexed from 0 to L−1 in a time order within an SSB burst set (i.e., half-frame). If L=8 or 64, three least significant bits (LSBs) b0 to b2 of the SSB index may be indicated by 8 different PBCH DMRS sequences. If L=64, three most significant bits (MSBs) b3 to b5 of the SSB index is indicated by the PBCH. If L=2, two LSBs b0 and b1 of an SSB index may be indicated by 4 different PBCH DMRS sequences. If L=4, the remaining one bit b2 except for two bits indicating an SSB index in 3-bit information which may be indicated by 8 PBCH DMRS sequences may be used for half-frame indication.

System Information Acquisition

FIG. 18 illustrates a system information (SI) acquisition procedure. The UE may obtain access stratum (AS)-/non-access stratum (NAS)-information in the SI acquisition procedure. The SI acquisition procedure may be applied to UEs in RRC_IDLE, RRC_INACTIVE, and RRC_CONNECTED states.

SI is divided into a master information block (MIB) and a plurality of system information blocks (SIBs). The MIB and the plurality of SIBs are further divided into minimum SI and other SI. The minimum SI may include the MIB and systemInformationBlock1 (SIB1), carrying basic information required for initial access and information required to obtain the other SI. SIB1 may also be referred to as remaining minimum system information (RMSI). For details, the following may be referred to.

-   -   The MIB includes information/parameters related to reception of         SIB1 and is transmitted on the PBCH of an SSB. The UE assumes         that a half-frame including an SSB is repeated every 20 ms         during initial cell selection. The UE may determine from the MIB         whether there is any control resource set (CORESET) for a         Type0-PDCCH common search space. The Type0-PDCCH common search         space is a kind of PDCCH search space and used to transmit a         PDCCH that schedules an SI message. In the presence of a         Type0-PDCCH common search space, the UE may determine (1) a         plurality of contiguous RBs and one or more consecutive symbols         included in a CORESET, and (ii) a PDCCH occasion (e.g., a         time-domain position at which a PDCCH is to be received), based         on information (e.g., pdcch-ConfigSIB1) included in the MIB. In         the absence of a Type0-PDCCH common search space,         pdcch-ConfigSIB1 provides information about a frequency position         at which the SSB/SIB1 exists and information about a frequency         range without any SSB/SIB1.     -   SIB1 includes information related to availability and scheduling         (e.g., a transmission periodicity and an SI-window size) of the         remaining SIBs (hereinafter, referred to as SIBx where x is an         integer equal to or larger than 2). For example, SIB1 may         indicate whether SIBx is broadcast periodically or in an         on-demand manner upon UE request. If SIBx is provided in the         on-demand manner, SIB1 may include information required for the         UE to transmit an SI request. A PDCCH that schedules SIB1 is         transmitted in the Type0-PDCCH common search space, and SIB1 is         transmitted on a PDSCH indicated by the PDCCH.     -   SIBx is included in an SI message and transmitted on a PDSCH.         Each SI message is transmitted within a periodic time window         (i.e., SI-window).

Beam Alignment

FIG. 19 illustrates exemplary multi-beam transmission of SSBs.

Beam sweeping refers to changing the beam (direction) of a wireless signal over time at a transmission reception point (TRP) (e.g., a BS/cell) (hereinafter, the terms beam and beam direction are interchangeably used). An SSB may be transmitted periodically by beam sweeping. In this case, SSB indexes are implicitly linked to SSB beams. An SSB beam may be changed on an SSB (index) basis or on an SS (index) group basis. In the latter, the same SSB beam is maintained in an SSB (index) group. That is, the transmission beam direction of an SSB is repeated for a plurality of successive SSBs. The maximum allowed transmission number L of an SSB in an SSB burst set is 4, 8 or 64 according to the frequency band of a carrier. Accordingly, the maximum number of SSB beams in the SSB burst set may be given according to the frequency band of a carrier as follows.

-   -   For frequency range of up to 3 GHz, maximum number of beams=4     -   For frequency range from 3 GHz to 6 GHz, maximum number of         beams=8     -   For frequency range from 6 GHz to 52.6 GHz, maximum number of         beams=64     -   Without multi-beam transmission, the number of SSB beams is 1.

When the UE attempts initial access to the BS, the UE may align beams with the BS based on an SSB. For example, the UE performs SSB detection and then identifies a best SSB. Subsequently, the UE may transmit an RACH preamble in PRACH resources linked/corresponding to the index (i.e., beam) of the best SSB. The SSB may also be used for beam alignment between the BS and the UE even after the initial access.

Channel Estimation and Rate-Matching

FIG. 20 illustrates an exemplary method of indicating actually transmitted SSBs, SSB_tx.

Up to L SSBs may be transmitted in an SSB burst set, and the number and positions of actually transmitted SSBs may be different for each BS or cell. The number and positions of actually transmitted SSBs are used for rate-matching and measurement, and information about actually transmitted SSBs is indicated as follows.

-   -   If the information is related to rate matching, the information         may be indicated by UE-specific RRC signaling or RMSI. The         UE-specific RRC signaling includes a full bitmap (e.g., of         length L) for frequency ranges below and above 6 GHz. The RMSI         includes a full bitmap for a frequency range below 6 GHz and a         compressed bitmap for a frequency range above 6 GHz, as         illustrated. Specifically, the information about actually         transmitted SSBs may be indicated by a group-bitmap (8 bits)+an         in-group bitmap (8 bits). Resources (e.g., REs) indicated by the         UE-specific RRC signaling or the RMSI may be reserved for SSB         transmission, and a PDSCH and/or a PUSCH may be rate-matched in         consideration of the SSB resources.     -   If the information is related to measurement, the network (e.g.,         BS) may indicate an SSB set to be measured within a measurement         period, when the UE is in RRC connected mode. The SSB set may be         indicated for each frequency layer. Without an indication of an         SSB set, a default SSB set is used. The default SSB set includes         all SSBs within the measurement period. An SSB set may be         indicated by a full bitmap (e.g., of length L) in RRC signaling.         When the UE is in RRC idle mode, the default SSB set is used.

FIG. 21 illustrates an example of a random access procedure. In particular, FIG. 21 shows a contention-based random access procedure.

First, the UE may transmit a random access preamble on a PRACH in UL as Msg1 of the random access procedure.

A random access preamble sequence may be supported to have two different lengths. A long sequence length of 839 may be applied to subcarrier spacings of 1.25 kHz and 5 kHz, and a short sequence length of 139 may be applied to subcarrier spacings of 15 kHz, 30 kHz, 60 kHz, and 120 kHz.

Multiple preamble formats may be defined by one or more RACH OFDM symbols and different cyclic prefixes (and/or guard times). A RACH configuration for a cell may be included in system information about the cell and provided to the UE. The RACH configuration may include information on the subcarrier spacing of the PRACH, available preambles, preamble formats, and so on. The RACH configuration may include information about association between SSBs and RACH (time-frequency) resources. The UE transmits the random access preamble on a RACH time-frequency resource associated with a detected or selected SSB.

The threshold of an SSB for RACH resource association may be configured by the network, and a RACH preamble may be transmitted or retransmitted based on an SSB where the RSRP, which is measured based on the SSB, satisfies the threshold. For example, the UE may select one SSB from among SSBs that satisfy the threshold and transmit or retransmit the RACH preamble based on a RACH resource associated with the selected SSB.

Upon receiving the random access preamble from the UE, the BS may transmit a random access response (RAR) message (Msg2) to the UE. A PDCCH scheduling a PDSCH carrying the RAR may be CRC masked with a random access (RA) radio network temporary identifier (RNTI) (RA-RNTI) and then transmitted. Upon detecting the PDCCH masked by the RA-RNTI, the UE may obtain the RAR from the PDSCH scheduled by DCI carried by the PDCCH. The UE may check whether the RAR includes RAR information in response to the preamble transmitted by the UE, i.e., Msg1. The presence or absence of the RAR information in response to Msg1 transmitted by the UE may be determined depending on whether there is a random access preamble ID for the preamble transmitted by the UE. If there is no response to Msg1, the UE may retransmit the RACH preamble within a predetermined number of times while performing power ramping. The UE may calculate PRACH transmit power for retransmitting the preamble based on the most recent path loss and power ramping counter.

If the UE receives the RAR information for itself on the PDSCH, the UE may obtain timing advance information for UL synchronization, an initial UL grant, a temporary cell RNTI (C-RNTI) from the RAR information. The timing advance information may be used to control a UL signal transmission timing. To align PUSCH/PUCCH transmission of the UE with the subframe timing of the network, the network (e.g., BS) may measure PUSCH/PUCCH/SRS reception and a subframe time difference therebetween and transmit the timing advance information based thereon. The UE may transmit a UL signal over a UL shared channel as Msg3 of the random access procedure based on the RAR information. Msg3 may include an RRC connection request and a UE identifier. In response to Msg3, the network may transmit Msg4, which may be treated as a contention resolution message on DL. Upon receiving Msg4, the UE may enter the RRC_CONNECTED state.

On the other hand, a contention-free random access procedure may be performed when the UE is handed over to another cell or BS or when it is requested by the BS. The basic principle of the contention-free random access procedure is similar to the contention-based random access procedure. However, in the contention-free random access procedure, a preamble to be used by the UE (hereinafter referred to as a dedicated random access preamble) is allocated to the UE by the BS, unlike the contention-based random access procedure in which the UE randomly selects a preamble to use from among a plurality of random access preambles. Information on the dedicated random access preamble may be included in an RRC message (e.g., handover command) or provided to the UE through a PDCCH order. When the random access procedure is initiated, the UE may transmit the dedicated random access preamble to the BS. When the UE receives an RAR from the BS, the random access procedure is completed.

As described above, a UL grant in the RAR may schedule PUSCH transmission to the UE. A PUSCH carrying initial UL transmission by the UL grant in the RAR is also referred to as an Msg3 PUSCH. The content of an RAR UL grant may start at the MSB and end at the LSB, and the content may be given as shown in Table 6.

TABLE 6 RAR UL grant field Number of bits Frequency hopping flag 1 Msg3 PUSCH frequency resource allocation 12 Msg3 PUSCH time resource allocation 4 Modulation and coding scheme (MCS) 4 Transmit power control (TPC) for Msg3 3 PUSCH CSI request 1

A TPC command is used to determine the transmit power of the Msg3 PUSCH. For example, the TPC command may be interpreted as shown in Table 7.

TABLE 7 TPC command value [dB] 0 −6 1 −4 2 −2 3 0 4 2 5 4 6 6 7 8

In the contention-free random access procedure, a CSI request field in the RAR UL grant may indicate whether the UE will include an aperiodic CSI report in corresponding PUSCH transmission. The subcarrier spacing for Msg3 PUSCH transmission may be provided by an RRC parameter. The UE may transmit the PRACH and the Msg3 PUSCH on the same UL carrier of the same serving cell. The UL BWP for the Msg3 PUSCH transmission may be indicated by system information block 1 (SIB1).

The NR system employs an OFDM transmission scheme or a similar transmission scheme. Specifically, the NR system may follow OFDM parameters different from those of LTE. The NR system may follow the legacy LTE/LTE-A numerology but have a larger system bandwidth (e.g., 100 MHz). Further, one cell may support a plurality of numerologies. That is, UEs operating with different numerologies may coexist within one cell.

FIG. 22 illustrates a structure of a radio frame used in NR.

In NR, UL and DL transmissions are configured in frames. The radio frame has a length of 10 ms and is defined as two 5-ms half-frames (HF). The half-frame is defined as five 1 ms subframes (SF). A subframe is divided into one or more slots, and the number of slots in a subframe depends on subcarrier spacing (SCS). Each slot includes 12 or 14 OFDM(A) symbols according to a cyclic prefix (CP). When a normal CP is used, each slot includes 14 symbols. When an extended CP is used, each slot includes 12 symbols. Here, the symbols may include OFDM symbols (or CP-OFDM symbols) and SC-FDMA symbols (or DFT-s-OFDM symbols).

Table 8 illustrates that the number of symbols per slot, the number of slots per frame, and the number of slots per subframe vary according to the SCS when the normal CP is used.

TABLE 8 SCS (15*2{circumflex over ( )}u) N^(slot) _(symb) N^(frame, u) _(slot) N^(subframe, u) _(slot) 15 KHz (u = 0) 14 10 1 30 KHz (u = 1) 14 20 2 60 KHz (u = 2) 14 40 4 120 KHz (u = 3) 14 80 8 240 KHz (u = 4) 14 160 16 * N^(slot) _(symb): Number of symbols in a slot * N^(frame, u) _(slot): Number of slots in a frame * N^(subframe, u) _(slot): Number of slots in a subframe

Table 9 illustrates that the number of symbols per slot, the number of slots per frame, and the number of slots per subframe vary according to the SCS when the extended CP is used.

TABLE 9 SCS (15*2{circumflex over ( )}u) N^(slot) _(symb) N^(frame, u) _(slot) N^(subframe, u) _(slot) 60 KHz (u = 2) 12 40 4

In the NR system, the OFDM(A) numerology (e.g., SCS, CP length, etc.) may be configured differently among a plurality of cells merged for one UE. Thus, the (absolute time) duration of a time resource (e.g., SF, slot or TTI) (referred to as a time unit (TU) for simplicity) composed of the same number of symbols may be set differently among the merged cells

FIG. 23 illustrates a slot structure of an NR frame. A slot includes a plurality of symbols in the time domain. For example, in the case of the normal CP, one slot includes seven symbols. On the other hand, in the case of the extended CP, one slot includes six symbols. A carrier includes a plurality of subcarriers in the frequency domain. A resource block (RB) is defined as a plurality of consecutive subcarriers (e.g., 12 consecutive subcarriers) in the frequency domain. A bandwidth part (BWP) is defined as a plurality of consecutive (P)RBs in the frequency domain and may correspond to one numerology (e.g., SCS, CP length, etc.). A carrier may include up to N (e.g., five) BWPs. Data communication is performed through an activated BWP, and only one BWP may be activated for one UE. In the resource grid, each element is referred to as a resource element (RE), and one complex symbol may be mapped thereto.

FIG. 24 illustrates a structure of a self-contained slot. In the NR system, a frame has a self-contained structure in which a DL control channel, DL or UL data, a UL control channel, and the like may all be contained in one slot. For example, the first N symbols (hereinafter, DL control region) in the slot may be used to transmit a DL control channel, and the last M symbols (hereinafter, UL control region) in the slot may be used to transmit a UL control channel. N and M are integers greater than or equal to 0. A resource region (hereinafter, a data region) that is between the DL control region and the UL control region may be used for DL data transmission or UL data transmission. For example, the following configuration may be considered. Respective sections are listed in a temporal order.

1. DL only configuration

2. UL only configuration

3. Mixed UL-DL configuration

-   -   DL region+Guard period (GP)+UL control region     -   DL control region+GP+UL region     -   DL region: (i) DL data region, (ii) DL control region+DL data         region     -   UL region: (i) UL data region, (ii) UL data region+UL control         region

The PDCCH may be transmitted in the DL control region, and the PDSCH may be transmitted in the DL data region. The PUCCH may be transmitted in the UL control region, and the PUSCH may be transmitted in the UL data region. Downlink control information (DCI), for example, DL data scheduling information, UL data scheduling information, and the like, may be transmitted on the PDCCH. Uplink control information (UCI), for example, ACK/NACK information about DL data, channel state information (CSI), and a scheduling request (SR), may be transmitted on the PUCCH. The GP provides a time gap in the process of the UE switching from the transmission mode to the reception mode or from the reception mode to the transmission mode. Some symbols at the time of switching from DL to UL within a subframe may be configured as the GP.

As more and more communication devices require high communication capacity, the efficient use of limited frequency bands becomes an important issue in wireless communication systems. In cellular systems including the LTE/NR system, a method of using U-bands widely used in the conventional Wi-Fi system such as the 2.4 GHz band or U-bands such as the 5/6 GHz band and 60 GHz band for traffic offloading is currently discussed. Basically, it is assumed that each communication node competes with other communication nodes to transmit and receive radio signals in U-bands. Thus, before transmitting a signal, each communication node needs to perform channel sensing to check whether other communication nodes perform signal transmission. In this document, the above operation is referred to as listen before talk (LBT) or channel access procedure (CAP).

In particular, an operation of checking whether other communication nodes perform signal transmission is referred to as carrier sensing (CS). When it is determined that there is no communication node performing signal transmission, it may be said that clear channel assessment (CCA) is confirmed. In the LTE/NR system, the BS or UE needs to perform LBT to transmit a signal in a U-band. In addition, when the BS or UE in the LTE/NR system performs signal transmission, other communication nodes such as a Wi-Fi node, etc. need to perform the LBT to avoid causing interference to the BS or UE. For example, in Wi-Fi specifications (801.11ac), a CCA threshold of −62 dBm is defined for a non-Wi-Fi signal, and a CCA threshold of −82 dBm is defined for a Wi-Fi signal. That is, when a station (STA) or an access point (AP) receives a non-Wi-Fi signal with power over −62 dBm, the STA or AP may not perform signal transmission to avoid causing interference.

The NR system supports transmission of one or more SS/PBCH blocks, and each SS/PBCH block has a specific index. The index of an SS/PBCH block may be obtained from sequence information in the corresponding SS/PBCH block and/or PBCH payload including a scrambling sequence. Accordingly, when the UE obtains the index of the corresponding SS/PBCH block from the information in the SS/PBCH block during initial access, the UE may recognize the time-domain boundaries of frames/subframes/slots and SS/PBCH block indices from a predetermined relationship between “SS/PBCH block indices” and “time-domain boundaries of frames/subframes/slots”. In addition, the UE may also recognize the indices of the frames/subframes/slots by combining other information in the SS/PBCH block. Further, the UE may perform RRM/RLM measurement for a serving cell and/or a neighbor cell for the purpose of mobility support, and in this case, the UE may require information about SS/PBCH blocks of the neighboring cell to perform measurement for each SS/PBCH block of the neighboring cell.

However, for random access in U-bands, since transmission is allowed only when the CAP is successful before the transmission, an SS/PBCH block that the BS desires to transmit at a specific time may not be transmitted. When the transmission of the SS/PBCH block is dropped, the time required for UEs attempting the initial access to camp on a cell may increase. In addition, the time required for UEs attempting serving/neighbor cell measurement to achieve meaningful measurement results may also increase.

Thus, a method of increasing the transmission opportunity of an SS/PBCH block where CAP failure is expected may be considered. From the perspective of the UE receiving the SS/PBCH block, a method of resolving ambiguity that may occur if the UE does not know when the BS succeeds in the CAP and transmits the SS/PBCH block may be considered. To this end, two methods may be considered as follows.

Method 1) Method of providing corresponding information through PBCH payload

Method 2) Method of providing delay information through specific sequence

Here, Method 1) and Method 2) may have the following advantages and disadvantages.

According to Method 1), although transmitted information has high reliability, but the receiver should perform PBCH decoding to obtain the information. In addition, when multi-cell interference is present, PBCH decoding performance is degraded, and thus, the time required to obtain the information may increase.

In Method 2), since ‘transmission time information’ is obtained by sequence detection, decoding performance may be superior compared to the PBCH decoding performance. Specifically, comparing the amount of information that may be transmitted by the PBCH payload and the sequence, the PBCH payload may include not only ‘transmission delay time information’ but also as various information related to the system, but the sequence may carry limited information including the ‘transmission delay time information’. In a multi-cell interference environment, the PBCH decoding performance may be degraded due to degradation of channel estimation performance, but the sequence may have a small decrease in the decoding performance, which is caused by the channel estimation performance degradation, so that the detection performance may be higher than that of the PBCH decoding.

In Method 2), the implementation of the UE may be relatively simple. When a delayed position due to LBT is represented by the sequence, the sequence is required as much as the delayed position. If ‘delay time information’, which is represented by M pieces, is additionally included in sequences used to transmit other information, the number of required sequences may be M times larger than N previously used sequences. That is, a total of N*M sequences may be used.

In other words, the number of required sequences may be a multiple of the number of pieces of information to be added, and thus, the UE should perform signal detection as many times as the multiple of the number of pieces of information to be added. For example, in the case of a PBCH DMRS sequence, 8 different sequences are used for each specific cell ID. If M pieces of time delay information due to LBT is transmitted based on the PBCH DMRS sequence, a total of 8*M PBCH DMRS sequences need to be used, which may burden the detection performance of the UE.

Considering that SS/PBCH block detection is performed in various cases such as initial cell detection, neighboring cell signal quality measurement, handover, and SCell/PSCell addition, a method that does not increase the burden of detection added in order for the UE to obtain information about when the BS starts SS/PBCH block transmission after succeeding in the CAP is required.

Accordingly, the present disclosure proposes a method of providing information about when the BS transmits the SS/PBCH block after succeeding in the CAP and a method by which the UE obtains information about a timing at which the SS/PBCH block is transmitted after receiving the corresponding SS/PBCH block.

The BS may transmit information about a point at which the SS/PBCH block is transmitted after succeeding in the CAP. In other words, if a candidate position in which a specific SS/PBCH block is capable of being transmitted is determined, the BS may include information on the corresponding candidate position in the SS/PBCH block and transmit the information to provide the candidate position to the UE. For example, when X SS/PBCH block indices are cyclically mapped to candidate positions, information on a position to which an SS/PBCH block index is mapped may be transmitted together with the corresponding SS/PBCH block index.

The UE, BS, and network according to the present disclosure may operate as shown in FIGS. 25 to 27.

First, the operations of the UE according to the present disclosure will be described with reference to FIG. 25.

Referring to FIG. 25, the UE may receive information on an ATSS that is actually transmitted among a plurality of SS/PBCH blocks (S2501). Then, the UE may receive an SS/PBCH block based on the ATSS information (S2503) and obtain information about the transmission timing of the SS/PBCH block based on the PBCH payload of the SS/PBCH block, a PBCH DMRS, and/or the phase of the SS/PBCH block (S2505). Particular operations of steps S2501 to S2505 will be described in the following embodiments.

The UE of FIG. 25 may be any one of various wireless devices shown in FIGS. 1 to 4. For example, the UE of FIG. 25 may be a first wireless device 100 of FIG. 1 or a wireless device 100 or 200 of FIG. 2. In other words, the operation processes of FIG. 25 may be performed and executed by any one of the various wireless devices illustrated in FIGS. 1 to 4.

Next, the operations of the BS according to the present disclosure will be described with reference to FIG. 26. Referring to FIG. 26, the BS may transmit information on an ATSS that is actually transmitted among a plurality of SS/PBCH blocks to the UE (S2601). The BS may perform a CAP for transmitting an SS/PBCH block in a U-band (S2603). If the CAP is successful, the BS may generate and transmit the SS/PBCH block based on the transmission timing of the SS/PBCH block and the ATSS information (S2605). Particular operations of steps S2601 to S2605 will be described in the following embodiments.

The BS of FIG. 26 may be any one of the various wireless devices shown in FIGS. 1 to 4. For example, the BS of FIG. 26 may be the first wireless device 100 of FIG. 1 or the wireless device 100 or 200 of FIG. 2. In other words, the operation processes of FIG. 26 may be performed and executed by any one of the various wireless devices illustrated in FIGS. 1 to 4.

FIG. 27 is a diagram illustrating the operations of the network according to the present disclosure. Referring to FIG. 27, the BS may transmit information on an ATSS that is actually transmitted among a plurality of SS/PBCH blocks to the UE (S2701). The BS may perform a CAP for transmitting an SS/PBCH block in a U-band (S2703). If the CAP is successful, the BS may generate and transmit the SS/PBCH block based on the transmission timing of the SS/PBCH block and the ATSS information (S2705). The UE may receive the SS/PBCH block based on the received ATSS information and obtain information about the transmission timing of the SS/PBCH block based on the PBCH payload of the SS/PBCH block, a PBCH DMRS, and/or the phase of the SS/PBCH block (S2707). Particular operations of steps S2701 to S2707 will be described in the following embodiments.

<Method of Providing Timing Information on SS/PBCH Block Through PBCH DMRS Sequence>

In the NR system, two SS/PBCH blocks are transmitted for each slot. For 15 kHz SCS, a total of 8 SS/PBCH blocks may be transmitted in slots #0, #1, #2, and #3, and the 8 SS/PBCH blocks may have indices of #0 to #7. Since these SS/PBCH blocks are arranged within a duration of 5 ms, 8 SS/PBCH blocks may be transmitted again in four slots, starting from the first slot of a next 5-ms duration after the 5-ms duration to which the SS/PBCH blocks of #0 to #7 are allocated. In other words, no SS/PBCH blocks are transmitted in slot #4.

For 30 kHz SCS, a total of 8 SS/PBCH blocks may be transmitted in slots #0, #1, #2, and #3, and the 8 SS/PBCH blocks may have indices of #0 to #7. Since the duration of slots #0 to #3 is 2 ms, no SS/PBCH blocks are transmitted in slots #4 to #9, and 8 SS/PBCH blocks may be transmitted again from slot #10, which is the starting slot of a next 5-ms duration.

If the total number of SS/PBCH blocks capable of being transmitted in NR-U is 4, SS/PBCH blocks with indices #0 to #3 may be repeatedly mapped twice to locations where SS/PBCH blocks with indices #0 to #7 are mapped. On the other hand, the indices of 8 SS/PBCH blocks may be obtained from PBCH DMRS sequences. That is, PBCH DMRS sequence indices #0 to #7 obtained from the PBCH DMRS sequences may be mapped one-to-one to SS/PBCH blocks having the same indices. As described above, if four SS/PBCH blocks are repeatedly mapped twice in NR-U, PBCH DMRS sequences with indices #4 to #7 may be mapped once more to SS/PBCH blocks with indices #0 to #3. For example, PBCH DMRS sequences with indices #0 and #4 may be mapped to an SS/PBCH block with index #0. That is, an SS/PBCH block corresponding to PBCH DMRS sequence #0 and an SS/PBCH block corresponding to PBCH DMRS sequence #4 may have the same index although the two blocks are received at different times. When SS/PBCH blocks have the same index, it may be interpreted to mean that the SS/PBCH blocks are transmitted on the same beam. That is, SS/PBCH blocks having the same index may be viewed as having a QCL relationship.

Therefore, the UE may acquire an SS/PBCH block index from a remainder obtained by dividing the SS/PBCH block index by a PBCH DMRS sequence index and identify a location at which the corresponding SS/PBCH block is transmitted from the PBCH DMRS sequence.

For example, referring to FIG. 28(a), when the BS fails in the CAP in slot number #0 but succeeds in the CAP in slot number #1, the BS may transmit SS/PBCH blocks in the beam order corresponding to SS/PBCH block indices #2, #3, #0, and #1. In this case, PBCH DMRS sequences may have indices #2, #3, #4, and #5. The UE performs correlation based on a total of 8 PBCH DMRS sequences in the same way as in licensed bands. If the correlation of a PBCH DMRS having a specific PBCH DMRS sequence index is measured above a predetermined value, the UE may obtain the transmission time of a SS/PBCH block based on an SS/PBCH block index related to the corresponding PBCH DMRS sequence index. If the UE detects PBCH DMRS sequence index #4, the UE may recognize that SS/PBCH block index #0 is received in slot number #2.

Referring to FIG. 28(b), a set of PBCH DMRS sequences used within a specific duration may be designated. For example, PBCH DMRS sequence indices #0 to #3 may be used in the first 5-ms duration of a duration of 10 ms, and PBCH DMRS sequence indices #4 to #7 may be used in the latter 5-ms duration. In other words, PBCH DMRS sequences may be used repeatedly in each 5-ms duration. If the BS succeeds in the CAP in the first 5-ms duration, the BS may transmit a PBCH DMRS based on a PBCH DMRS sequence set (e.g., PBCH DMRS sequence indices #0 to #4) used within the first 5-ms duration. The UE may attempt to detect a signal based on 8 PBCH DMRS sequences and obtain SS/PBCH block indices and information about the 5-ms duration based on the indices of detected PBCH DMRS sequences. Further, a method of indicating a value for shifting SS/PBCH block indices cyclically within a specific duration may be applied together.

<Method of Providing Timing Information on SS/PBCH Block by Changing Phases of OFDM Symbols to which SS/PBCH Block is Mapped>

If the BS designates a plurality of candidate times for transmitting SS/PBCH blocks, the BS may change and transmit information about several signals included in the SS/PBCH blocks over time.

For example, the phase of a PBCH RE (i.e., both a DMRS RE and a data RE or only a PBCH DMRS RE) may be inverted and transmitted. In this case, the PBCH RE may mean both a DMRS RE and a PBCH data RE or only a PBCH DMRS RE.

For example, referring to FIG. 29, in cyclic index 0, transmission may be performed with the current phase (+), and in cyclic index 1, transmission may be performed by multiplying the inverted phase (−). Upon receiving an SSS and a PBCH DMRS transmitted by the BS, the UE may estimate a radio channel from each signal and measure the strength of the SSS and DMRS based on the estimated channel. In this case, by comparing the phase of radio channel information estimated from the SSS and the phase of radio channel information estimated from the PBCH DMRS, the UE may obtain time information about the corresponding SS/PBCH block.

For example, referring to FIG. 28(a), a PBCH may be transmitted with the current phase (+) in the first 5-ms duration, and a PBCH may be transmitted with the inverted phase (−) in the latter 5-ms duration. The UE may obtain information about the first or latter 5-ms duration by comparing the phases of estimated radio channels.

In one embodiment, referring to FIG. 29, the phases of a PBCH DMRS RE and a PBCH data RE mapped to the second and fourth OFDM symbols may be changed, and the phases of a PBCH DMRS RE, a PBCH data RE, and an SSS mapped to the third OFDM symbol may not be changed.

In another embodiment, referring to FIG. 29, the phases of a PBCH DMRS RE and a PBCH data RE mapped to the second, third, and fourth OFDM symbols may be changed, and the phase of an SSS mapped to the third OFDM symbol may not be changed.

The phase change in the PBCH RE and/or SSS may be used to inform a group of DMRS sequences. For example, a PBCH DMRS sequence group used to identify the transmission positions of SS/PBCH blocks within a total duration of 5 ms in which the SS/PBCH blocks are capable of being transmitted may be recognized based the above-described phase change. For example, referring to FIG. 30(a), a PBCH DMRS sequence group capable of being transmitted in slot numbers #0 to #3 and a PBCH DMRS sequence group capable of being transmitted in slot numbers #4 to #7 may be identified by the phases of SS/PBCH blocks. For example, if the phase of an SS/PBCH block is +1, the UE may recognize that the corresponding SS/PBCH block is transmitted in slot numbers #0 to #3. If the phase of an SS/PBCH block is −1, the UE may recognize that the corresponding SS/PBCH block is transmitted in slot numbers #4 to #7.

If the phase change shown in FIG. 29 is subdivided according to modulation schemes such as QPSK, 8PSK, 16PSK, etc., more information may be provided.

For example, referring to FIGS. 30 and 31, when there are a total of four positions for cyclic mapping as shown in FIGS. 30(a) and 30(b), transmission may be performed by changing the phases in cyclic indices #0 to #3 by +1, +j, −1, and −j, respectively. For example, referring to FIG. 30(a), when the number of PBCH DMRS sequences is greater than the number of SS/PBCH block indices, a delayed position index may be provided by the PBCH DMRS sequence and phase change information. For example, referring to FIG. 30(a), if SS/PBCH block index #0 is transmitted in slot number #2, the BS may generate PBCH DMRS sequence index #4 and, at the same time, change the phase of a PBCH RE by +1. The UE may detect that the index of the PBCH DMRS sequence transmitted by the BS is #4 based on 8 candidate PBDH DMRS sequences. In addition, by comparing the phase change of the PBCH RE, the UE may recognize that the index of the transmitted SS/PBCH block is #0 and the SS/PBCH block is transmitted in slot number #2.

Referring to FIGS. 30(b) and 31(b), when there are a total of N positions for cyclic mapping, SS/PBCH blocks may be transmitted by changing the phases in cyclic indices #0 to #N−1 by expj(2pi*n/N) (where n=0, . . . , N−1), respectively. For example, FIG. 30(b) shows a case where N=4, and FIG. 31(b) shows a case where N=5.

For example, referring to FIGS. 30(a) and 31(a), when the number of PBCH DMRS sequences is greater than the number of SS/PBCH block indices, a delayed position index may be provided by the PBCH DMRS sequence and phase change information. For example, referring to FIGS. 30(a) and 31(a), if SS/PBCH block index #0 is transmitted in slot number #2, the BS may generate PBCH DMRS sequence index #4 and, at the same time, change the phase of a PBCH RE by +1. The UE may detect that the index of the PBCH DMRS sequence transmitted by the BS is #4 based on 8 candidate PBDH DMRS sequences. In addition, by comparing the phase change of the PBCH RE, the UE may recognize that the index of the transmitted SS/PBCH block is #0 and the SS/PBCH block is transmitted in slot number #2. As shown in FIG. 31(a), if the PBCH DMRS sequence is repeated M times, the phase of the PBCH RE may be changed by expj(2pi*m/M) (m=0, . . . , M−1). Specifically, if the PBCH DMRS sequence is repeated twice as shown in FIG. 30(a), M=2. If the PBCH DMRS sequence is repeated three times as shown in FIG. 31(a), M=3.

On the other hand, as shown in FIGS. 30 and 31, when 8 PBCH DMRS sequences are repeated twice, two slots among a total of 10 slots or four candidate positions among a total of 20 candidate positions may remain. In this case, the remaining slots or positions may be left empty as shown in FIG. 30, or the PBCH DMRS sequence may be repeated as many times as the remaining slots or positions as shown in FIG. 31.

<Method of Providing ATSS Information in U-Band>

In the NR system, a different sequence may be used for each OFDM symbol in a duration of 10 ms. Thus, when an SS/PBCH block is transmitted in a specific slot, a sequence mapped to an OFDM symbol in the corresponding slot in which the SS/PBCH block is transmitted due to the success of the CAP may be transmitted. In other words, the UE may obtain the index of the SS/PBCH block from a PBCH DMRS and obtain the slot index and/or the OFDM symbol index from another additional sequence.

Alternatively, an additional sequence defined for each cyclic index may be used, and when the SS/PBCH block is transmitted, the defined additional sequence may be transmitted together. In other words, if the BS succeeds in the CAP, the BS may transmit the additional sequence for the cyclic index corresponding to a time when the SS/PBCH block is transmitted. The UE may detect the SS/PBCH block index and the cyclic index so that the UE may obtain the SS/PBCH block index and the transmission time of the SS/PBCH block. The additional sequence may be QCLed with a related SS/PBCH block and transmitted together with the related SS/PBCH block in a half frame. The above-described additional sequence may be transmitted in all or some of the OFDM symbols in which SS/PBCH blocks are transmitted. The UE may detect the additional sequence based on information about a time/frequency/spatial resource in which a specific SS/PBCH block is received.

In a U-band, SS/PBCH blocks may be transmitted at predetermined candidate times, and the transmittable candidate time of each SS/PBCH block may be determined for each index. A candidate time at which an SS/PBCH block may be transmitted regardless of the SS/PBCH block index may be referred to as a location index. The index of an SS/PBCH block transmitted in a specific location index may be obtained from detection of a PBCH DMRS sequence and/or additional sequence, phase comparison between SS/PBCH blocks, and/or PBCH content. In this document, the location index may be replaced with the SS/PBCH block index, and the SS/PBCH block index may be replaced with the beam index or QCL information. In this case, if the index of the SS/PBCH block corresponds to QCL information, it may be assumed that SS/PBCH blocks having the same SS/PBCH block index are transmitted on beams having the same index.

FIGS. 32 and 33 are diagrams for explaining a relationship between the location index and the SS/PBCH block index.

Referring to FIGS. 32 and 33, when an SS/PBCH block is transmitted in a duration of 5 ms, a maximum of 10 candidate locations for transmitting the SS/PBCH block may be configured in 5 slots for 15 kHz SCS, and a maximum of 20 candidate locations may be configured in 10 slots for 30 kHz SCS. In other words, the candidate locations for transmitting the SS/PBCH block may have indices #0 to #9 for the 15 kHz SCS and may have indices #0 to #19 for the 30 kHz SCS.

In the case of a conventional SS/PBCH block, a PBCH DMRS may include up to 8 sequences. To indicate the indices of the candidate locations as described above, the number of PBCH DMRS sequences may increase. Thus, the candidate locations of SS/PBCH blocks may be mapped to PBCH DMRS sequences.

For example, assuming that there are a total of 10 PBCH DMRS sequences, for the 15 kHz SCS, the PBCH DMRS sequences may be mapped to candidate locations with indices #0 to #9. The SS/PBCH block candidate locations with indices #0 to #9 may be configured in slot numbers #0 to #4 and/or slot numbers #5 to #9. Each of PBCH DMRS sequences #0 to #9 may be mapped to each candidate location. When the BS transmits the SS/PBCH block in a slot location where the LBT or CAP is successful, the BS may transmit a PBCH DMRS sequence for a candidate location in which the corresponding SS/PBCH block is actually transmitted.

Alternatively, when the SS/PBCH block is transmitted in the slot position where the CAP or LBT is successful, an SS/PBCH block index corresponding to a candidate location determined according to the value of Q may be used as the SS/PBCH block index that the BS intends to indicate to the UE. For example, the SS/PBCH block index may be used as the initial seed value of a PBCH scrambling sequence. On the other hand, the above-described Q value may mean an interval between SS/PBCHs where QCL may be assumed. For example, the Q value is an interval in which SS/PBCH blocks with the same transmission beam (Tx beam) may be remapped, and this interval may be represented by N durations with respect to the candidate location index. For example, if Q=1, it may be assumed that candidate location indices 0, 1, 2, 3, 4, . . . etc. are QCLed. If Q=2, it may be assumed that candidate location indices 0, 2, 4, 6, 8, . . . are QCLed. If Q=4, it may be assumed that candidate location indices 0, 4, 8, . . . are QCLed. If Q=5, it may be assumed that candidate location indices 0, 8, . . . are QCLed.

For the 30 kHz SCS, PBCH DMRS sequences may be mapped to candidate locations with indices #0 to #19. However, when the number of PBCH DMRS sequences is less than the number of candidate locations, PBCH DMRS sequence indices #0 to #9 may be mapped to candidate location indices #0 to #9 and candidate location indices #10 to #19. To distinguish mapping to first 10 candidate locations #0 to #9 and mapping to next 10 candidate locations #10 to #19, the phases of PBCH symbols may be changed.

Meanwhile, the maximum number of transmittable SSBs may be determined for each frequency band. For U-band transmission, a plurality of candidate locations where the SS/PBCH block may be transmitted due to the LBT or CAP may be designated, and a distance capable of assuming the same QCL condition among the designated candidate locations may be defined.

In the current NR system, the length of a bitmap of actually transmitted SS/PBCH block (ATSS) indices indicated by SIB1 and UE-specific RRC signaling is determined according to the maximum number of SS/PBCH blocks, and the length of a bitmap for designating SS/PBCH blocks to be measured by a measurement object is also determined.

However, considering the positions of SS/PBCH blocks where the same QCL may be assumed as described above, if there are a maximum of 8 SS/PBCH blocks, an 8-bit bitmap may be required, but if the Q value is less than 8, the size of the bitmap for ATSS indication may be reduced than 8 bits. For example, when Q is 4, a 4-bit bitmap may be used.

Alternatively, the UE may maintain the bitmap size configured according to the maximum number of SS/PBCH blocks as it is. The UE may recognize that some bits of the bitmap are valid based on the number of bits in a QCL duration determined according to the Q value and not interpret the remaining values.

For example, if Q is 4, the BS transmits an 8-bit bitmap to the UE for the ATSS indication. However, since only the first four bits among 8 bits are valid, the UE may use the first four bits to obtain ATSS information. In this case, the last four bits may be filled with ‘0’. That is, the BS may indicate the ATSS through the above-described bitmap, and the UE may perform rate matching, SSB to RACH Occasion (RO) mapping, and so on based on the value of the bitmap. The BS may designate measurement target SS/PBCH blocks through the reconfigured bitmap, and the UE may measure the corresponding SS/PBCH blocks based on the value of the corresponding bitmap.

In the case of LTE-NR DC, NR-NR DC, or SPCell and/or SCell addition, the value of Q may be indicated by UE-specific RRC signaling (e.g., ServingCellConfigCommon), and in this case, ATSS Information may also be provided. Bits for the ATSS information may be determined according to the value of Q as described above. When the bit size is maintained equal to the existing value, the UE may interpret only a valid area.

It is obvious that each of the examples of the proposed methods may also be included as one implementation method, and thus each example may be regarded as a kind of proposed method. Although the above-described embodiments may be implemented independently, some of the embodiments may be combined and implemented. In addition, it may be regulated that information on whether the embodiments are applied (or information on rules related to the embodiments) are transmitted from the BS to the UE through a predefined signal (e.g., a physical layer signal, a higher layer signal, etc.).

The various details, functions, procedures, proposals, methods, and/or operational flowcharts described in this document may be applied to a variety of fields that require wireless communication/connection (e.g., 5G) between devices.

Hereinafter, a description will be given in detail with reference to drawings. In the following drawings/descriptions, the same reference numerals may denote the same or corresponding hardware blocks, software blocks, or functional blocks unless specified otherwise.

FIG. 34 illustrates a communication system 1 applied to the present disclosure.

Referring to FIG. 34, the communication system 1 applied to the present disclosure includes wireless devices, BSs, and a network. A wireless device is a device performing communication using radio access technology (RAT) (e.g., 5G NR (or New RAT) or LTE), also referred to as a communication/radio/5G device. The wireless devices may include, not limited to, a robot 100 a, vehicles 100 b-1 and 100 b-2, an extended reality (XR) device 100 c, a hand-held device 100 d, a home appliance 100 e, an IoT device 100 f, and an artificial intelligence (AI) device/server 400. For example, the vehicles may include a vehicle having a wireless communication function, an autonomous driving vehicle, and a vehicle capable of vehicle-to-vehicle (V2V) communication. Herein, the vehicles may include an unmanned aerial vehicle (UAV) (e.g., a drone). The XR device may include an augmented reality (AR)/virtual reality (VR)/mixed reality (MR) device and may be implemented in the form of a head-mounted device (HMD), a head-up display (HUD) mounted in a vehicle, a television (TV), a smartphone, a computer, a wearable device, a home appliance, a digital signage, a vehicle, a robot, and so on. The hand-held device may include a smartphone, a smart pad, a wearable device (e.g., a smart watch or smart glasses), and a computer (e.g., a laptop). The home appliance may include a TV, a refrigerator, a washing machine, and so on. The IoT device may include a sensor, a smart meter, and so on. For example, the BSs and the network may be implemented as wireless devices, and a specific wireless device 200 a may operate as a BS/network node for other wireless devices.

The wireless devices 100 a to 100 f may be connected to the network 300 via the BSs 200. An AI technology may be applied to the wireless devices 100 a to 100 f, and the wireless devices 100 a to 100 f may be connected to the AI server 400 via the network 300. The network 300 may be configured using a 3G network, a 4G (e.g., LTE) network, or a 5G (e.g., NR) network. Although the wireless devices 100 a to 100 f may communicate with each other through the BSs 200/network 300, the wireless devices 100 a to 100 f may perform direct communication (e.g., sidelink communication) with each other without intervention of the BSs/network. For example, the vehicles 100 b-1 and 100 b-2 may perform direct communication (e.g. V2V/vehicle-to-everything (V2X) communication). The IoT device (e.g., a sensor) may perform direct communication with other IoT devices (e.g., sensors) or other wireless devices 100 a to 100 f.

Wireless communication/connections 150 a, 150 b, and 150 c may be established between the wireless devices 100 a to 100 f/BS 200 and between the BSs 200. Herein, the wireless communication/connections may be established through various RATs (e.g., 5G NR) such as UL/DL communication 150 a, sidelink communication 150 b (or, D2D communication), or inter-BS communication (e.g. relay or integrated access backhaul (IAB)). Wireless signals may be transmitted and received between the wireless devices, between the wireless devices and the BSs, and between the BSs through the wireless communication/connections 150 a, 150 b, and 150 c. For example, signals may be transmitted and receive don various physical channels through the wireless communication/connections 150 a, 150 b and 150 c. To this end, at least a part of various configuration information configuring processes, various signal processing processes (e.g., channel encoding/decoding, modulation/demodulation, and resource mapping/demapping), and resource allocation processes, for transmitting/receiving wireless signals, may be performed based on the various proposals of the present disclosure.

The embodiments of the present disclosure described herein below are combinations of elements and features of the present disclosure. The elements or features may be considered selective unless otherwise mentioned. Each element or feature may be practiced without being combined with other elements or features. Further, an embodiment of the present disclosure may be constructed by combining parts of the elements and/or features. Operation orders described in embodiments of the present disclosure may be rearranged. Some constructions of any one embodiment may be included in another embodiment and may be replaced with corresponding constructions of another embodiment. It will be obvious to those skilled in the art that claims that are not explicitly cited in each other in the appended claims may be presented in combination as an embodiment of the present disclosure or included as a new claim by a subsequent amendment after the application is filed.

In the embodiments of the present disclosure, a description is made centering on a data transmission and reception relationship among a BS, a relay, and an MS. In some cases, a specific operation described as performed by the BS may be performed by an upper node of the BS. Namely, it is apparent that, in a network comprised of a plurality of network nodes including a BS, various operations performed for communication with an MS may be performed by the BS, or network nodes other than the BS. The term ‘BS’ may be replaced with the term ‘fixed station’, ‘Node B’, ‘enhanced Node B (eNode B or eNB)’, ‘access point’, etc.

Those skilled in the art will appreciate that the present disclosure may be carried out in other specific ways than those set forth herein without departing from the spirit and essential characteristics of the present disclosure. The above embodiments are therefore to be construed in all aspects as illustrative and not restrictive. The scope of the disclosure should be determined by the appended claims and their legal equivalents, not by the above description, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein.

While the method and apparatus for transmitting and receiving a DL signal have been described above in the context of being applied to a 5G New RAT system, they are also applicable to various wireless communication system as well as the 5G New RAT system. 

1. A method of receiving, by a user equipment (UE), a synchronization signal/physical broadcast channel (SS/PBCH) block in an unlicensed band, the method comprising: receiving information on an actual transmitted SS/PBCH block (ATSS) transmitted from a base station; and receiving the SS/PBCH block based on valid bits among a plurality of bits included in the information on the ATSS, wherein the valid bits are configured based on that the number of the valid bits is determined by an interval value between SS/PBCH blocks for which QCL (Quasi Co-Location) can be assumed, wherein the reception of the SS/PBCH block is performed based on that SS/PBCH block indexes for the unlicensed band are indicated by the valid bits, and wherein the number of the SS/PBCH block indexes is equal to the number of the valid bits.
 2. The method of claim 1, wherein among the plurality of bits, bits except the valid bits are not interpreted.
 3. The method of claim 1, wherein among the plurality of bits, bits except the valid bits have a value of ‘0’.
 4. The method of claim 1, wherein the number of the valid bits is equal to the interval between the SS/PBCH blocks in which the QCL assumption is allowed.
 5. The method of claim 1, further comprising performing rate matching for a physical downlink shared channel (PDSCH) or mapping between the SS/PBCH block and a random access channel (RACH) occasion based on the valid bits.
 6. The method of claim 4, wherein the valid bits include as many bits as the number of the SS/PBCH block indices from a first bit among the plurality of bits.
 7. The method of claim 1, wherein the UE is configured to communicate with at least one of the base station, a UE other than the UE, a network, or an autonomous driving vehicle.
 8. A device configured to receive a synchronization signal/physical broadcast channel (SS/PBCH) block in an unlicensed band, the device comprising: at least one processor; and at least one memory operably connected to the at least one processor and configured to store instructions that, when executed, cause the at least one processor to perform operations comprising: receiving information on an actual transmitted SS/PBCH block (ATSS) transmitted from a base station; and receiving the SS/PBCH block based on valid bits among a plurality of bits included in the information on the ATSS, wherein the valid bits are configured based on that the number of the valid bits is determined by an interval value between SS/PBCH blocks for which QCL (Quasi Co-Location) can be assumed, wherein the reception of the SS/PBCH block is performed based on that SS/PBCH block indexes for the unlicensed band are indicated by the valid bits, and wherein the number of the SS/PBCH block indexes is equal to the number of the valid bits.
 9. The device of claim 8, wherein among the plurality of bits, bits except the valid bits are not interpreted.
 10. The device of claim 8, wherein among the plurality of bits, bits except the valid bits have a value of ‘0’.
 11. The device of claim 8, wherein the number of the valid bits is equal to the interval between the SS/PBCH blocks in which the QCL assumption is allowed.
 12. The device of claim 8, wherein the operations further comprise: performing rate matching for a physical downlink shared channel (PDSCH) or mapping between the SS/PBCH block and a random access channel (RACH) occasion based on the valid bits.
 13. The device of claim 11, wherein the valid bits include as many bits as the number of the SS/PBCH block indices from a first bit among the plurality of bits.
 14. The device of claim 8, wherein the device is configured to communicate with at least one of the base station, a user equipment (UE), a network, or an autonomous driving vehicle.
 15. A user equipment (UE) configured to receive a synchronization signal/physical broadcast channel (SS/PBCH) block in an unlicensed band, the UE comprising: at least one transceiver; at least one processor; and at least one memory operably connected to the at least one processor and configured to store instructions that, when executed, cause the at least one processor to perform operations comprising: receiving information on an actual transmitted SS/PBCH block (ATSS) transmitted from a base station through the at least one transceiver; and receiving the SS/PBCH block through the at least one transceiver based on valid bits among a plurality of bits included in the information on the ATSS, wherein the valid bits are configured based on that the number of the valid bits is determined by an interval value between SS/PBCH blocks for which QCL (Quasi Co-Location) can be assumed, wherein the reception of the SS/PBCH block is performed based on that SS/PBCH block indexes for the unlicensed band are indicated by the valid bits, and wherein the number of the SS/PBCH block indexes is equal to the number of the valid bits. 